Examples here
https://www.acoustimac.com/acoustic-panels/acoustic-panels-dmd-series
I've done a few with my own photos printed on them, they look like canvas art. Well, they basically are, but also filled with sound deadening insulation.
I will probably make some myself at custom sizes, it's basically a frame filled with insulation from the big box store, wrapped in fabric.
The impact they have is reducing room reverb, which helps a lot for conversation when there are a lot of people in the room.
Not a bad idea. The hardest part I think would be getting the insulation to the right thickness to fit. Not sure how well it cuts.
Most art probably isn't very thick either, and 2" thick is a sweet spot because it works better at low frequencies, but isn't excessively large