Get a painting done for that wall with a frame that is deep enough to encompass that electrical box (why do electricians and architects do this!??) and hang the picture over the box. It has to be able to be easily removed of course, in case you need to get into the electrical box. In the second photo you posted, that is exactly the size I would do, and notice it is also in a deep straight edge frame.

I have the same problem on two walls ! On one wall I hung a large painting ( they are light , remove when needed which at most is twice a year ) and on the other Wall I added a collage of photos where one of the photos gets taken off when access is needed . NO problem at all . Or you could put a sliding door with a painting attached over it ...and the same molding on the bottom as the wall .

By code are you allowed to cover it in any way? Maybe design this artwork to be on a hinge like a cabinet door so it EASILY is accessible.