I don't know for painting, but there is this interesting dev journal about architecture :

https://chroniclesofelyria.com/forum/topic/1203/dj-14-player-housing-architecture-construction

Quite a while back I had an idea which was an attempt to stay true to the 'player skill + character skill' approach to skills, in relation to art.

It was essentially like a screenshot system - you'd be able to capture an image of your own POV (or perhaps a slightly unleashed POV for the sake of more freedom of angles, etc) which would then be converted into a canvas which you had to fill in yourself. Depending on your player skill you could succeed / fail in filling in the lines, in using the appropriate colours, or just outright making poor / bad composition when taking the shot in the first place. That way, character skill could be then integrated by making the tools more difficult to use the less achieved you were as a painter.

I also like it because it would have properly integrated art into the world (i.e. you genuinely sit on a hill and paint the scenery, rather than all art having to be 'artificial' in that sense), and it sorts out the concern of griefing, as the process makes it harder to just draw a penis. That isn't to say that you could not have a freeform drawing system, but it's a possibility.