You need to add texture to the wall. You should either add a ledge stone from floor to ceiling, or a travertine tile. It will give the room a wow factor. I would have suggested a wood mantel but with the tv above the fireplace would make it look busy.

I would consider this wall the focal in the room considering all of the elements (angled, tv and fireplace ) therefore I would go for a darker color and would not do the red. consider a dark taupe or dark warm grey.

good luck,
M.M.

i got a couple of pictures of a stone that would look great in your space on my page under fireplaces