If you take a job as a painter or sculptor, through City Hall (self-employ), after some time the paintings or sculptures you create will show up in the art gallery that's the default in the town.
I'm not sure about the "grey square" problem other than asking if your graphics card/driver could be upgraded. I've not seen that happen before, save when just entering a lot (after I've overhauled the buildings/homes in the town with nicer interiors/decor). I suppose my card needs a bit of time to catch up.
Barring that I would assume the premise would be simply to create a community lot building and have a Sim visit and place the art from their inventory. Sculptures, you would have to use "testingcheatsenabled true" and shift-click the lot and select "build/buy on this lot" to allow access to family inventory, where the sculptures are stored.
Sorry, I know this probably isn't much help. Good luck, and a nice idea. If it's figured out I may have to try it
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