I would not do it. It puts unnecessary strain on your neck or forces people to lie back like the dead and it's hard enough to teach my kids to not slouch. You might not think the neck thing matters but we all get old .. if we're lucky. It also makes me feel like I'm in a bar, an airport, or a bad restaurant. Sorry, if that offends anyone, it's how I feel and so far all of my clients have agreed without needing any persuasion.But that doesn't mean it's wrong to do it. Only the owner's family needs to like it. To me it's just not that difficult to put the TV to one side with the great adjustable brackets now available. The proper height of a TV is easy to determine, just sit on a couch, look straight ahead, and have someone measure the point you feel comfortable looking at. Perhaps take an average of your family members. If I had to do it, I would at least put the fireplace box tight to the floor, the mantel low, and be able to enclose the TV when not in use. These things are not pretty. It would also help to recess it and tip it downward for better viewing and less reflected light. I was in an Italian restaurant in the 60's called Charlie's that had multiple gas fireplaces recessed into the wall above seated head height. Would that work?

Sammie J, I meant what surrounds the gas fireplace insert, and also the column to the left of the cabinetry. Right now it looks somewhat like concrete, too, but perhaps more like concrete tiles. I wonder if I should cast the whole thing in concrete. Thanks.

I actually think they did a prettty good job with height. Most are much higher. I am not a fan typically of the design because of the height but this one is good. In my one recessed location (not above a fireplace, I made it so tight with drywall, the ledge material didn't matter (just drywall). Something to consider. I would think whatever you do, you want it to be easily modified.

We have a frame TV over our fireplace. As long as you have a way to run the cable so it's unobtrusive, it looks just like a piece of art. We bought the frame (which needs to be purchased separately) from deco frames. Don't put a huge TV there unless you don't care about proportion. If you are keeping the hearth, I would try to get brick to match. If you don't have a tech tube, create something above the fireplace to run cables (shiplap/paneling).