I've found a file on my computer when I was cleaning documents up with information according to what influence traits may have on the outcome of paintings. I have no idea where I got it, but it seems important for the members among us from which sims where busy with the paint skill.
Could be that this information already is somewhere on this forum. If so, feel free to remove this topic fellow mods.
For what it's worth: I've created that file on 27-04-2010 23;04;03 PM.
Here is the info that it contains:
No Trait - If your sim has no other traits, he will always paint the basic version of the painting.
Artistic - Gives a water-color effect to the painting, though with highlighted border effects on the object of the painting.
Can't Stand Art - Darkens the painting with higher contrast and heavier, thicker brush strokes.
Computer Whiz - Gives the painting a square-tiled effect, obliterating any detail.
Evil - Tints the picture heavily towards red, most details are left intact.
Grumpy - Tints the picture heavily towards blue, most details are left intact.
Genius - Tiles the picture into small white-bordered hexagons/pentagons.
Insane - Obliterates detail, makes colors more flat and contrasting, shapes become jagged.
Neurotic - Turns the painting into a bright neon mess.
Virtuoso - Adds a white flair effect to the painting, most details are left intact.