Do you sell your masterpieces and artifacts?

Course. Need Simoleons.

I usually sell the masterpieces, but sometimes I keep one that I think just looks good with the look of the house and put it up on a wall. As for artifacts, despite having bought JA a couple months ago, I have yet to spend sims on an archaeological expedition, but I might put a few in a museum lot and sell the rest.

The majority of art I sell. But I usually keep the ones I like

That's how most of my sims earn their livings.