For the Angevin Empire, in no particular order:
For Traditions; +10% Infantry combat ability, to represent the longbows which allowed England to dominate the French at Agincourt, and +2 max cultures embraced, to represent their successful control of so many cultures.
Empire in Naught but Name; While chroniclers already sing songs of the Angevin Empire, we are neither united nor centralised enough to truly claim an imperial title, this must be rectified. +5 states, -5% development cost and -5% build cost.
Treaty of Falaise; The treaty signed by King William the 1st of Scotland, had William officially swear that Scotland would be subordinate to the English Crown, that English soldiers would garrison important Scottish towns, and that Scotland would pay for their upkeep. +15% vassal tax and -10% diplo annexation cost.

French Law but English Rule; England's law is different from village to village, and crimes on this side of the channel are nothing on the other, this must be stopped. If nothing else, French laws are worth enforcing and we shall see our realm unified under it. +0.5 yearly Prestige, -0.10 monthly autonomy.
Divide the Nobility; By splitting the lands of the nobility between England and France we can reduce their influence, and with their lands separated, they will have a hard time rising up against us. -2 national unrest.
Lords of Ireland and Wales; While enforcing our rule over these realms was difficult initially, now that they recognise their place under our rule, they are allowed some autonomy, in return for greater military support. +10% manpower recovery +10% max manpower.

Economic Fluidity; From Chinon Castle we administer the realm's entire economy. English taxes are used to improve our holdings on the continent, while our Norman, Breton and Celtic taxes build Britain to greater and greater prosperity. +15% national taxes
The Humiliation of France; In the year 1154, the King of England officially ruled more of France than the French King and now that is true again, the very foundation of our empire is built on our superiority over those across our Channel, even more recently we annihilated the French army at Agincourt, England is better than France! +15% morale of armies.
For the Ambition, either 5% discipline or -10 culture conversion cost.

For Illyria;
No real ideas for the traditions, but given their position, +1.5% missionary strength and +1 diplomatic reputation, for converting provinces, and gaining allies against the Ottomans and Habsburgs.
More than just a Region; Never before has Illyria been a true state, merely a region, populated by many cultures and tribes, and while many kingdoms have risen in the area, never before has Illyria been truly united as it is now. -0.10 monthly autonomy
More than just Balkan; Despite our unity, many other nations refuse to see us as anything more than just another Balkan state, soon to splinter. We refuse this reputation, and will make them pay for their assumptions. +30% hostile core creation and -10% core creation cost.

More Powerful Than They Think; Since Rome first conquered Illyria, our great land has been passed around from country to country, never being allowed to proper under the rule of one of our own. With an Illyrian finally leading us, people are more than happy to show their support. +15% max manpower, +10% max force limit.
More Impressive Than They Know; The Illyrian Kingdoms lasted for 700 years before Rome came for our land, and while it pains us to admit, Rome has turned a splintered but strong land, into one that is both stronger and more united. +5% discipline and +10% national taxes.
More Than the Sum of our Parts:Serbia, Bosnia, Montenegro, Ragusa, all nations that claimed this great land, for only they knew it's real worth. There will be no more infighting, no more petty squabbles, the only thing in our future is greatness: +1 yearly prestige +1 yearly legitimacy.

More Foreward Thinking than all Others; Knowing our past, we will innevitably cause the attention of others to turn our way, we must be prepared. Plans will be put in place, areas of engagement decided years in advance, and new technolgies swiftly integrated into our nation. +25% defensiveness and -15% institution embracement cost.
No More: No more will we fear the enemies at our gates. No more will our land be ridiculed, with names such as prefecture and region. No more will Heathens, heretics and foreigners, decide who lives and who dies. When they wake in hell, they shall find it empty, for all the Devils, now walk the Earth. +10% Infantry Combat ability, +10% Cavalry Combat ability.
Either +10% Artillery combat ability, or -10% Aggresive Expansion impact, depending on your preference.

@DeathShade
Thanks, this is good content!

LAT_ideas:1 "Romanian Ideas"
LAT_ideas_start:1 "Romanian Traditions"
LAT_ideas_bonus:1 "Romanian Ambition"

(I use this because because is called like Empire of Romania here : https://en.wikipedia.org/wiki/Latin_Empire )

I also use this flag: http://oi67.tinypic.com/2a519vm.jpg (Purple is the imperial colour.The most associated color with Roman Emperor Clothing is the color purple. Only a Roman Emperor was allowed to wear the 'trabea' which was a toga entirely colored in purple and worn on ceremonial occasions.)

LAT_ideas = {
start = {
infantry_power = 0.1
core_creation = -0.25
}

bonus = {
culture_conversion_cost = -0.25
}

trigger = {
tag = LAT
}

free = yes #will be added at load.

the_crusader_tradition = {
army_tradition = 0.5
army_tradition_decay = -0.01
}

crusade_for_anatolia = {
discipline = 0.05
land_morale = 0.05
}

knights_of_christ = {
global_missionary_strength = 0.01
extra_manpower_at_religious_war = yes
}

greek_schoolars_lae = {
technology_cost = -0.05
idea_cost = -0.05
}

byzantine_bureaucracy = {
advisor_cost = -0.1
state_maintenance_modifier = -0.25
}

support_latin_trade = {
merchants = 1
trade_efficiency = 0.1
}

the_latin_emperor = {
legitimacy = 0.5
prestige = 0.5
}
}

(VEF description):

the_crusader_tradition: "Crusader Tradition"
the_crusader_tradition_desc: "\"We are a crusader state - true successor to the Roman Empire, and blessed by God to bring destruction to all heathens and heretics. We are the warriors of the Lord.\""
knights_of_christ: "Knights of Christ"
knights_of_christ_desc: "Our duty to this land is to spread the word of Christ. This is our sacred vow, and we will die for our lord, as he died for us."
byzantine_bureaucracy: "Byzantine Bureaucracy"
byzantine_bureaucracy_desc: "While the Byzantines are worthy of nothing but distrust, their empire has brought about much great thinking. We must adopt their tenets for the good of the nation."
support_latin_trade: "Support Latin Trade"
support_latin_trade_desc: "The great city of Constantinople is a center for much art and trade. Supporting traders, regardless of nationality, will help consolidate our power within the Greek seas."
greek_schoolars_lae: "Greek Scholars"
greek_schoolars_lae_desc: "Across these great lands lie great people. The Greeks - known for their philosophic, mathematic, and scientific exploits - must be redeemed for our empire to thrive."
crusade_for_anatolia: "Crusade for Anatolia"
crusade_for_anatolia_desc: "The Turks have controlled Anatolia for far too long. As the heirs to ancient Roman lands, we must drive a crusade against the Turks, and remove them once and for all."
the_latin_emperor: "The Latin Emperor"
the_latin_emperor_desc: "We have become victorious where the once-great Roman Empire failed. Now we are the true rulers of the Latin people, the true Emperor, and the very voice of God."

@tullio25
Thanks, I will definitly use the ideas!

Well, maybe you will think improveing the Roman's. Here is a mod made by me but is not published yet.(I have some problems with the localisations that i can't figure. PS I tried with 0 but it doesn't work) You can use it if you like.
{LINK REMOVED}http://www.mediafire.com/file/kn7t9d5fpnrbk1z/Romans.zip

I will think about the Székely Land and the Saxonland? (translyvanian Saxon) ideas as well.

@tullio25
Your localization files need to be in UTF-8 BOM encoding, you have them in UTF-8.
I would put in the 0 to, as Paradox tells us that it needs it.

You can change the encoding in Notepad ++, save and try mod again to see if it works.

I'm using a mac so i can't install Notepad. I have a default program that was ok until the 0 change happened. I tried to download a similar program (TextWrangler) but is not doing the job. I don't know how to get UTF-8 BOM encoding so... i can't do mods anymore (the localisation part)...

But i can cheat a little :). Here are the ideas/flags and all other staff for the Szekely and Saxons:
{LINK REMOVED}http://www.mediafire.com/file/536egqud6hx6hfy/Transylvania.zip
(The ideas are from other nation that exist in vanila)

SSS_ideas = {
# Sasz Ideas
start = {
hostile_attrition = 1.0
trade_efficiency = 0.1
}

bonus = {
merchants = 1
}

trigger = {
tag = SSS
}
free = yes

# Transylvanian Saxons
# In the 12th century the Hungarian King Géza II invited Germans to settle and defend the relatively sparsely populated Transylvanian region. These 'Transylvanian Saxons' developed their areas quickly, and made the soil arable, improved agricultural methods, and exploited areas containing precious metals and salt deposits.
transylvanian_saxons = {
build_cost = -0.1
}
# Zunft
# Guilds specific to every sort of craft are founded to insure the quality of products and to train young artisans.
zunft = {
production_efficiency = 0.1
}
# Reform the Army
# The German knights, veterans from crusades and countless European wars are simply not numerous enough to remain the base of our armies. Now we must reorganize the army to pave way for domestically levied regiments, capable of replacing the knights on the battlefield.
teu_idea_1 = {
cavalry_cost = -0.1
infantry_cost = -0.1
}
# Recruit Peasants
# It has become clear to us that we can no longer rely on foreign volunteers to fill up our army ranks. No matter how experienced and valuable they might be. Instead a system that would allow us to levy our subjects, Germans and non-Germans, must be developed.
teu_idea_2 = {
manpower_recovery_speed = 0.15
}
# Unio Trium Nationum
# Unio Trium Nationum was an alliance established in 1438 by the three Transylvanian Estates. The Hungarian nobility, the Saxon merchants, and the free military Szeklers. The union was a pact directed against the peasantry, many of whom were Romanian. This alliance would have a long lasting and unexpected impact on the history of our people."
unio_trium_nationum = {
cavalry_power = 0.15
}
# PUnitarian Zeal
# The Unitarian church is a Reform movement started at the same time in Transylvania and Poland. The adoption of this new branch of the Reformation is going very swift in our lands, especially after the Patent of Toleration
unitarian_zeal = {
tolerance_own = 2
}
# Anti-Habsburg Policies
# George I Rákóczi, prince of Transylvania tried to strengthen his position against the opposing claimants to the Transylvanian lands, the Habsburg, by joining the Swedish in the 30 years war against the Austrian Holy Roman Emperor. He successfully occupied Upper Hungary and was sieging Brno when the Ottoman sultan ordered him to cease the hostilities against the Habsburgs
anti_habsburg_policies = {
diplomatic_upkeep = 1
}
}

SSC_ideas = {
# Szekely Ideas
start = {
mercenary_cost = -0.25
merc_maintenance_modifier = -0.25
}

#
bonus = {
possible_mercenaries = 0.25
}

trigger = {
tag = SSC
}
free = yes

# Vlachs
# The sheep-herding inhabitants of the Carpathian mountains, the Vlachs, are an inherently hard to influence population group resenting all change and cherishing the old Balkan traditions. In the times of trouble they anchor us in our past reminding us who we are and who we have been.
vlach_shepherds = {
enemy_core_creation = 0.25
}
# Holy Order
# Only the purest of faith can be become a foot soldier in the army of Christ. To be pure in mind, spirit, and body requires not just a man who is heaven bound but also a superior warrior. These soldiers will form the nucleus of an army that will stand against anyone who dares to attack us
holy_order = {
discipline = 0.05
}
# Land of Castles
# Some say we have more castles per person than any other region in the world but given our many powerful neighbors who can blame us? We must be true to this legacy and never leave a border unguarded or our castles understaffed. This is surely the best way to safeguard our independence in a dangerous world!
slo_land_of_castles = {
fort_maintenance_modifier = -0.1
garrison_size = 0.1
}
# Recruit Peasants
# It has become clear to us that we can no longer rely on foreign volunteers to fill up our army ranks. No matter how experienced and valuable they might be. Instead a system that would allow us to levy our subjects, Germans and non-Germans, must be developed.
teu_idea_2 = {
manpower_recovery_speed = 0.15
}
# Unio Trium Nationum
# Unio Trium Nationum was an alliance established in 1438 by the three Transylvanian Estates. The Hungarian nobility, the Saxon merchants, and the free military Szeklers. The union was a pact directed against the peasantry, many of whom were Romanian. This alliance would have a long lasting and unexpected impact on the history of our people."
unio_trium_nationum = {
cavalry_power = 0.15
}
# PUnitarian Zeal
# The Unitarian church is a Reform movement started at the same time in Transylvania and Poland. The adoption of this new branch of the Reformation is going very swift in our lands, especially after the Patent of Toleration
unitarian_zeal = {
tolerance_own = 2
}
# Anti-Habsburg Policies
# George I Rákóczi, prince of Transylvania tried to strengthen his position against the opposing claimants to the Transylvanian lands, the Habsburg, by joining the Swedish in the 30 years war against the Austrian Holy Roman Emperor. He successfully occupied Upper Hungary and was sieging Brno when the Ottoman sultan ordered him to cease the hostilities against the Habsburgs
anti_habsburg_policies = {
diplomatic_upkeep = 1
}
}

Well, im so bad with the ideas, and with the traditions, but i have many countries <3

-Egiptian Empire
-French Empire (like Napoleon)
-Macedonian Empire
-Sparta
-Gupta Empire
-Athens
-Tebas
-Etruria
-Epiro
-Umayyad Caliphate
-Fatimid Caliphate
-Almoravid Caliphate
-Padania
-North Italian Confederation (is true, thanks to Visconti)
-Akkadian Empire
-Babilonian Empire
-Asirian Empire
-Hittite Empire
-Minoic Empire (great development and great float)
-Mycenean Empire
-Mauryan Empire
-Rashtrakute Empire
-Republic of Cartage
-Kingdom of Israel
-Kingdom of Jerusalen
-Scythian Empire
-Tracian Empire
-Kingdom of Phoenicia
-Indo-Aryan Empire
-Kush Empire
-Dacian Empire
-Han Empire
-Funan
-Srivijaya
-Seleucid Empire
-Sassanid Empire
-Visigoth Kingdom
-Ostrogoth Kingdom
-Celt Empire
-Avar Empire
-Cossack Empire
-Kingdom of Asturias
-Yugoslavia
-United Slav Nation
Well, maybe later, if i have the time, i can post the ideas and the traditions, sorry, i cant now, but thank you for this <3

Dacia was not an empire. In time of Burebista was the most powerful until the Romans conquer 1/3 of the land in 101-102 and 105-106 (the wars between emperor Trajan and king Decebal).It was a revenge because the empire was paying tribute to Dacia or maybe because Trajan was thinking that the Thracians was the ancestors of Rome.
https://en.wikipedia.org/wiki/Dacia
I included them in the second post.

i know that Dacia was not an empire, but im triying to say that, if you are Romania, or Valachia, you can form Dacia as an empire.

Ah, anoter idea, Seljuk Empire

I already know history. But, sorry if i post the same idea, well, Dacian Empire is your idea <3