Thanks everyone, katluvr, glad you like my collections and find a good use for them! SimCityBusDriver, TheChronicr is right about cheat parts, I used Static Needs to speed things up. But there needed to be some strategy involved. I have my Sim started painting, than cancel the action and move on to next easel, until he got 30 unique paintings, then he finished them and max painting during that. Once the Brushmaster challenge is done Sim can't finish paintings he started before it, which make things difficult since most paintings are on lower levels. So I had to marry him, have the wife paint her round, then their 2 children too. My Muse Family is very talented even if none is artistic and they split the task evenly!
Tip for regular players is that most of the paintings are unlocked between levels 4 and 8, and some paintings are unavailable after Sim max skill even if unlocked (painted earlier). I was disappointed that my main Sim simply never started new paintings available around level 7 and 8 after maxing skill, he keep repeating those he already painted.
Anyway glad you like it, and feel free to use them as decoration or whatever you find them usefull for.