Some ideas Riverlands

Braavosi Water Dancers - Skirmishers with good City Terrain bonuses. Buffs against Heavy Infantry.

Trident Knights- Riverland Heavy Cav MAA, heavy version of Trident Scouts

Riverrun Riders - Heavy Cav for Riverrun Title. Expensive and slightly better version of the Trident Knigts.

Pinkmaiden Wardens - Pretty-boy Heavy Infantry for Pinkmaiden title.

Seagard Sentinels - Either Heavy Infantry/ Heavy Cav for Seaguard. Defend region from Ironborn raids.

Ironwood Sentinels/ Dragon Fire Remnants - Heavy Cav or Heavy infantry for Harrenhal. Lots of armor and heavy upkeep.

Andal Faithful - Heavy Cav or Heavy Infantry for either Stony Sept, Wayfarers Rest, Andalos. Andal Knights similar to those from the Andal invasions.

Crown Guardsmen - Pikemen from Rosby/Duskendale region. Constables that keep the peace between settlements.

Excellent, it's about time we've been waiting for new units from the Riverlands.

Some eventual addition ideas by region:

Riverlands:
The Poolguard- House Mooton spearmen
The Strong Arms- House Strong Heavy Infantry

The Westerlands:
The Hooded Men- House Banefort Light Cavalry, with a spooky motif

Dorne:
?-House Uller- Probably some sort of Anti Dragon Siege Weapon or Crossbowmen

The Reach:
Thematically something Bull related to House Bulwer- Probably Heavy Cav or Infantry

The Stormlands:
The Griffin Talons- House Connington Heavy Cavalry
The Sapphire Stalwarts- Heavy Cav or Heavy Infantry for House Tarth
The Felwood Forresters- Archers or Light Infantry

I'm pretty sure House Santagar in the north-east of Dorne has the only tiles with Jungle Terrain in Westeros. Jaguar-themed warriors with Jungle buffs would be cool. Spotted Stalkers would be a cool name if they are themed as ambush units.

Some ideas focusing on the Stormlands, I'm thinking about creating them myself but I have 0 modding experience and can't draw worth a lick.

Stormlands:
Knights of Storms End- Heavy Cav for House Baratheon
Stormguard- Heavy Infantry for House Baratheon
Wardens of Shipbreaker Bay- Pikemen for all Stormlanders
Kingswood Skirmishers- Skirmishers for all Stormlanders
Weepers of Cape Wrath- Crossbowmen for all Stormlanders
Wendwater Scouts- Light Cavalry for all Stormlanders
Bronzegate Pikes- Pikemen for House Buckler
Greenstone Sliders- Skirmishers/Archers for House Estermont
Knights of the Evenstar- Heavy Cav for House Tarth
Sapphire Blades- Heavy Inf for House Tarth
Sentinels of Evenfall Hall- Archers/Spearmen for House Tarth
Knights of the Roost- Heavy Infantry/Heavy Cav for House Connington
Rooster Arrows- Archers for House Connington
Dondarrion Outriders- Light Cavalry for House Dondarrion
Cockleswhent Harvesters- Archers/Skirmishers/Horse Archer for House Selmy
Knights of the Harvest- Heavy Cav/Heavy Inf for House Selmy
Fell Knights- Heavy Inf/Heavy Cav for House Felwood
Swann Knights- Heavy Cav for House Swann
The Nightingales- Archers for House Caron