Amber, with all the business already going on w/the fireplace, are you sure you want more things around it? just what I see, your mantel surround, (the 3-sided white piece) is too small. proportionally, it's just not right. (to see what I mean, look at this pic. very similar FP. ignore the decor. just look at how the surround properly fits the stone tile work)

your mantel is more of a traditional looking piece that belongs to another type of FP. And the little mantel items look like miniatures sitting under the tv. I don't mind a tv above the fp (others despise it) but what is going on w/the gray/white accenting? you have what appears to be a travertine type stone in very warm pinks/browns, and then a blue/gray accent paint color above, mixed in w/more gray on the wall.

I think this is the look you want? rather that break up the height w/color, use the white all the way, w/the trim work. and notice how the surround fits the FP, along w/the full mantel. this type of surround would look better on yours.

you have a gorgeous tall ceiling and I assume some windows, and this small fireplace. I just think with what you have, it can be reworked a little better. here are a few photos to show you what I mean. take a look, and if you don't like them, you can tell me to pound.

these are similar set-ups to your room

this is similar to your trim work,,it's just spread out a bit. it's blurry,,,but notice the surround and proportion to everything around the FP.

It feels like mantle day here. Beth's ideas are all headed in the right direction.

Nice room and fireplace. Would, at the very least paint that small, solid white rectangle, most of which is just above the tv, the same darker color as that part of the accent wall above the mantel/tv to make it visually disappear -- even if it is a over a speaker.

Without the tv atop the mantel, the accent wall "works" -- and works well; however, with the tv blocking a bottom chunk of that wall accent, it creates an uneven effect so you might at least consider painting the white trim the darker color, too. (Definitely would not add a huge hulking mirror or art over it.)

My thinking about decorations on the mantel is that EITHER you keep the tv above the mantel … and nothing else ,,, OR you decorate above the mantel.

If the tv suits you where it is, then add a pair of bookshelves or curio cabinets -- one on each side of the fireplace.

For better symmetry, take some measurements before choosing those cabinets so you can keep the tops of these bookshelves or cabinets approximately the same height as the top of your mantel -- even if you need to add feet or wheels to the cabinets or add a shelf beneath the tv.

Do either completely cover or not cover at all (with the tops of your cabinets/shelves) the two rectangles on the walls on each side of the tv.