Visually the problem isn't the space above, but the fact that the TV is floating midway between floor and ceiling and not "grounded".

This is a 75" TV, also in a room with 12 ft ceilings. I did a built in, but the TV is "grounded" to the cabinet "console" below it. Bottom of TV is 40" off the floor.

I thought of something like that but couldn't figure out what to put there because of the window on the left. If I did built-in shelves around it (or wainscoting), would it look too much with the window there? I thought it would be too "busy" if that makes sense. The wall to the left is a fireplace and that kind of anchors the room a bit too 🥴

Get a longer/taller/deeper console, move it back against the wall and lower the TV. Conceal the wires.

Don't go with gray again. I think a wood stain would be better to tie into the rest of the wood in the room.

Awesome advice! But then I still have a massive area above the TV with nothing on it

Not every space has to have stuff on it. Decorate the the lower 8 ft properly and there will be no need to clutter the upper walls.

Look up negative space in Interior design.

https://www.homesandgardens.com/news/negative-space-in-interior-design

What chispa said … also have someone ( our handyman did it ) conceal the wires from the TV, concealed them within the wall. A much cleaner look.

Add vertical elements such as plants in tall planters (you already have some, just scale up a bit), narrow built-in cabinets or vertical bookshelves

Or

Nothing is needed above the tv - in fact, the tv is too high. I agree with the other posters. There’s no need to decorate space above your head.

Nothing is needed on the wall, aside from a longer TV console. We'd also suggest moving the plant stand elsewhere. Note the long TV console used in this living room design of ours below:

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