are you able to mount the tv on another wall, or is the only place for it? If you can mount the tv on the wall opposing the couch I would do that - then turn that niche into a custom book shelf. You could put a beautiful geometric modern wall paper to make that niche pop (or a nice paint color) and carry that over to the niche on top of the fireplace. The image here is not your configuration, but I think this idea could work. Also avoid using the top of your mantle for small pieces and "clutter" put 1-2 larger pieces of art (large vase, etc.) so you can turn that area into more of a design element. If you can't move the TV consider building shelving to hold it and get rid of the table.