In those games it deletes the sim in question (I've played sims 3 pets console only though so if you have a different version your mileage may vary) which may glitch the paintings but my guess is that if you are playing that version that the 10 day period you have before they become unplayable also makes the paintings that they've painted get the marker that the artist has died and I have had a painter die like that and their work became worth more right off the bat until I resurrected them.
I suggest just starving them if you want the paintings to go up in value and you also want them out of the household and then clicking on them once they become controllable and send them to the netherworld to remove them.
I hope this helps.