Uli said:
Never expect a response in less than 24 hours.
No there isn't guides for specifically adding paintings but its not hard. Just need to replicate the painting frame/model you want to use and adjust the texture for it and then you're done.
You will have to wait for someone else to reply for a better explanation on it and a bit more of a hand holding explanation.
don't mind Uli, underneath his gruff exterior he really is a GREAT help and resource for those of us still learning.
BUT... Big BUT... You need to be willing to use that big brain of yours to glean his bits and pieces of input.
So the biggest first Question is do you want to add a new painting, or modify an existing. While the process of making the painting itself is the same, there's a whole new set of skills you will need to feed that back into core3 if it's a new item...
-Duff