A shelf holding black and white frames of various sizes would look very nice on the wall along the length of the couch.

You could do a collage of art pieces.

art is very personal.

if you do have something custom, try to pull in the warm tones of the rug.

this orange chair and tall plant would look great w/your rug. also, notice the artwork.

why don't you look on Etsy for custom pieces? also, think about doing a tall plant in that corner. or:

shelves, as mentioned

you could always pull things forward a bit and do something like this behind it. don't forget the plants!

As long as you go big - a blank wall would be better than little dinky stuff...