Aha! So that explains why lots with custom sim-paintings crash the game when trying to use them without the sim that made the paintings. If sim-created paintings are tied to the sims' character files, then that very much makes sense. Well, you learn something new every day.
I have a community lot with a bunch of custom paintings on it, the sim that made them is not even in the current hood this lot is in now. It has never crashed on me. It also hasn't crashed in a friends hood.
The lot was bought, paintings were placed, lot was sold back to community.