I wouldn't spend any money on a temporary solution. Just leave it as is and put your money toward putting up the shelves.

I'd really love the tv so much more if it were positioned above one of the shelves rather than the fireplace. It would change the height scale and allow you to not feel the need to 'decorate' the area as much. As for furniture, can you move the couch/rug away from the wall, centered on the fp and have the flow of traffic run behind it? It would downplay the doorways opening onto the space and make the room more cozy/oriented towards the built ins(which are very lovely). Just some thoughts....

The TV is too high. Put it over either set of shelves. Balance the non-TV side with a similar-sized painting or a grouping of four smaller pieces. An attractive mirror would work well above the mantel.

The TV is too high, and it's making your ceiling feel lower than it is. Move it to one side over the cabinets, and then create symmetry by putting a piece of art over the other side.

I'm not sure it makes any sense to worry about shelves etc unless you work out a reasonable furnishings arrangement for this room. I also agree that the TV is mounted too high for a room this small.

Rooms this size have to have flexible furnishings and that includes chairs that swivel. Sizing of furnishings is critical. Here are two possible new layouts for your room, because what you currently is not working.

https://www.amazon.com/Danya-GH073-Pipe-Shelves-Brown/dp/B071XFSG1M

Thanks everyone for your thoughts so far! Curious for those suggesting moving the TV, are you just not "tv over the fireplace" people? I know there's a strong POV by some that it's a bad idea in general. I ask because I'm trying to understand if there's something specific about my room that makes it a bad idea and if so, what those characteristics are. I really like how it looks in the below examples and my tv doesn't appear to be any higher than these rooms since my ceilings are 8ft and these ceilings look higher.

https://www.houzz.com/photos/project-in-tiburon-traditional-family-room-san-francisco-phvw-vp~298646

https://www.houzz.com/photos/ullswater-traditional-family-room-raleigh-phvw-vp~137896

https://www.cnet.com/how-to/dont-mount-a-tv-above-a-fireplace/

So, this is the TV room and the room next door is...

I agree with Sina. IMO the TV's are too high in your example pics, too. As Sina mentioned, the height of your TV is giving the illusion of a lower ceiling...something I noticed right away. Most mantels can look so much nicer with art or other decor above them instead of a big black TV hanging there. However, you should do what works best for you. There are certainly lots of TV's above lots of mantels. Lots of sore necks, too.

Room next door in picture 3 is the front, more formal sitting room. Unfortunately it's too sunny to put the TV in there. I'd love to tear down that wall between the 2 rooms which would give us more flexibility in the furniture layout but it's a load-bearing wall and we're not prepared to take that level of renovation on.

Every few months this gets posted, but TV mounting if often initiated by the men in the household and their decision of where to mount the TV is heavily influenced by the sports bars they frequent.

Move T.V to the one cabinet it will still be a bit high but much better then hang a nice laerge piece of art above the other one you are done

Respectfully, is there any chance back to being about wall decor? While I definitely see the POV that TVs don't belong over fireplaces and appreciate the numerous resources that have been offered, per the example images I provided, I really like the appearance of a TV over the fireplace. Based on the large number of images available on Houzz and other sites where this set-up exists, there are at least some people out there who feel the same. After doing some more digging, based on pictures I'm finding, it seems that flanking the center with symmetrical art is most common.

https://www.houzz.com/photos/christie-lane-makeover-contemporary-living-room-phvw-vp~74925949

https://www.houzz.com/photos/jane-lockhart-interior-design-kylemore-model-home-dublin-traditional-living-room-toronto-phvw-vp~1267470

Respecting your desire to keep TV over fireplace, I would suggest two large decorative mirrors on either side. Perhaps a sophisticated version of the “window pane” mirrors that are popular now.

Continuing my previous comment suggesting mirrors:
https://www.potterybarn.com/products/trellis-wood-rectangular-mirror-black/?pkey=call-mirrors&isx=0.0.2013
Or

https://www.potterybarn.com/products/trellis-wood-rectangular-mirror-black/?pkey=call-mirrors&isx=0.0.2013#viewLargerHeroOverlay

For now, I would find art work to hang over the cabinets. The pros here can help you more with that...maybe a large canvas over each cabinet. I would remove the candle holders from the mantel...you don't need anything else with the TV there. Once you find art work for the walls, you can decide what, if anything, to place on top of the cabinets. Keep it simple...not a lot of small items.

Save your money for proper shelving. You are, of course, correct, lots of photos of TVs above fireplaces. But the rooms are definitely larger than yours. Your home, so, of course, do what you want, but pay attention to how comfortable you feel after an evening binging on Netflix. The angle between the TV and your eyes is too great for your narrow room. Can you reposition the sofa and chair? The sofa placed perpendicular to the fireplace, and the chair flanking the fireplace, with the TV on the wall where the chair is now?

Jeeezzzz....the poster likes the TV where it's AT!.... Move on about the TV.