I would hang T.V. lower than you are planning the center of the screen should be at eyelevel I would get rid of all those shelves new and old and hang a great piece of art on that wall and of course painted a new color IMO some shade of gray from the fireplace stone as for storage for T.V stuff a very shallow low cabinet would work look at Besta from Ikea you could maybe even use some on the wall under the art work I would not build a mantle on this fireplace keep it simple

I wouldn't paint the stone. A lot of what is making it feel unbalanced are all of those little shelves and accents around the fireplace. That white light on the soffit, all of the shelves to the left, and even the fixture near the shelves: all of these little accents compared to the large stone facade doesn't equal out. Well-designed built ins could help, or, I would consider painting the room a lighter color and embracing the look/feel of the stone fireplace and placing a large, modern piece of art on the wall to the left, TV looks good where you placed it. It would need something below it to balance the look.