I think the patrons coming need to be staggered, so that you have time to prepare. Either that, or you need more artists. I think that the paintings need to cost more based on your prestige and the difficulty level/time it took to make it. Maybe a bonus for doing it early (having time left on it). There's no way to tell if someone is tired until they're ZZZing, so I think there needs to be a bar for that attached to the other info you get when you mouse over one of the artists. If it's not in place already (I didn't spend too much time focusing on whether there was a difference) I suggest compounding the done part of the painting when more than one artist is working on it. Like other people have suggested, I think having another artist in the mix and/or making the payments for the portraits more would make it easier. The studying part seems really harsh for no reason--you lose mastery of the craft when you practice the craft? I don't really get it.
I didn't do a lot with the shop because I never had enough money, so I can't really speak on that point.
I love the little news tidbits you have in there. I also love the fact that the portraits are of the people buying them. I hope you continue developing this wonderful little game into something more! It's definitely fun to play.