Usually people just seem to post their mods and leave it to the moderators to decide
and the latter by my impression only check mods once they get reported.

As far as i know there are no rules on mod content, outside copyright, license, DLC requirements and respecting other modders work etc.
See links at the bottom of this post.


Paradox rules for anything are usualy phrased in such a unspecific way, that it's hard to tell
how a moderator would act in case and that's on purpose to keep a free hand.
Basically Paradox is a Dictatorship....., but with quite arbitrary rules.

Unless someone else shows up that knows and i doubt it, i'd suggest to ask the question in the Paradox Forum and there either in Paradox General Discussion
https://forum.paradoxplaza.com/forum/forums/paradox-general-discussion.518/
or in the Forum/Help subforum, though the latter is usually only for specific questions regarding that specific forum, so PDX General rather. IF you are hellbent to get an official response that is.


Now back on the specific points you made :

Lewd descriptions should not realy be a problem, generallly speaking.
The game itself and other mods contain that too.

Images i don't know. Depends i guess.

What i recall is that a pornographic mod once got deleted from the Workshop, but i'm not perfectly sure if that was due to moderators or the mod author, but i think the former.
This mod though went into SM territorry and more, so i could have been more related to violence gone too far in depiction and action, than to sex itself. Might also have gone into gender hate, usually with CK2 it's about torturing and killing men.Of the latter kind i think only one mod of that type survived until this day, which i haven't used though and only read the description. Another is bordering that, but you can do it to both genders and it's pretty historically plausible too to a degree and not really hateful in it's form. So still in line with all the disgusting things that can be done in CK2.

As the game itself is rather violent and has a lot of clear sexual references *cough*, softporn regarding the images should likely be okay, but i can't guarantee it. Which is probably about the response you would get on the official forum.


Official rules :

This is the now old and closed thread on CK2 mod rules :
https://forum.paradoxplaza.com/forum/threads/rules-for-user-made-mods-edits.779854/

This is the still open one in general for mods on PDX games with updated rules :
https://forum.paradoxplaza.com/forum/threads/updated-14-06-18-rules-for-user-made-mods-and-edits-of-pds-games.708039/