Sheet rock

For the time being just remove everything from the high shelf and lower the two outside pictures and mount them on either side of TV, like l-l, the l's being the pictures and the hyphen the TV. Use the third picture elsewhere. This will lower the focal point level and you won't notice the high shelf as much.

Try to ignore the niche after removing everything from it. If you cannot then drywall over it as BNH suggested. Some accents of architecture have been added in the hopes of adding interest, instead they just add confusion.

HI -- Have it filled in with drywall and be done with it . If that space cannot be used on the other side if there is a room . Don't decorate something you hate so much .

Thank you for the advice! I think black vases would make it look a lot better. I don't really want to sheet rock it. Just want to have it flow with the rest of the space... Right now it's just a little awkward.

Take all the stuff off it and ignore it...

Black vases are going to compete with your art. Don't put anything there if you are not willing to sheetrock over it.