what about adding some shelves?

How about putting the TV on a taller table. Or if you can afford a built-in cabinet, incorporate the TV into it. I wouldn't put the TV above the fireplace -- too big.

Wall mount the T.V so the top is level with the mantel it will be a better viewing height add a cabinet under it that matches the mantel and then see if a couple of shelves above are needed.

It is not a very big living room and I'm afraid that mounting the tv above the fire place would put the tv at an uncomfortable height where you have to look up when watching tv. I've attach another picture so you can see the layout of the living room. The sofa sits directly across the nook where the tv is. And yes, that wall is bare too

The fire place starts right where the wall ends/arch start on the opposite side.

I would mount the TV in the nook with a cool wallpaper print behind it. Then I would remove the table with a bench that's flesh with the nook

I would purchase a two-door cabinet which fits into the nook and either matches the wood on the fireplace or is painted in your accent color or a color from the brick. Place the tv on the cabinet and add shelves above the tv (same color as the cabinet) to hold some books, framed art and/or some crafted item you love. Adding doors on the nook would make the room feel small, so open shelving would be better looking.