I would try a navy blue or dark gray paint on the wall over the fireplace. Maybe just go up the color chip card from the rest of the walls to the darkest version on the card? It will help the tv blend in and the color pops on the tv when you are watching it. We watch a lot of sports at our house and my husband swears by a darker wall behind the television.

The other option you might try is covering the wall above the fireplace in weathered wood. We used a product on my office walls that was easy to install and relatively inexpensive. http://www.homedepot.com/p/Timeline-Wood-11-32-in-x-5-5-in-x-47-5-in-Distressed-Grey-Wood-Panels-6-Pack-00957/205791534

I would try washing the mantel with a grey stain.