I’d say go for it - paint is easy to work with and inexpensive

My first thought is no but after looking at your mockup I've changed my mind to maybe. The mocked up tv is essentially changing the color of a large portion of the wall. Isn't hard to imagine that being extended to each corner. Would suggest you go darker as you have with the mock up. Perhaps a charcoal gray would work.

Or maybe extend to paining the entire wall?

I think a dark wall (or accent piece) will make the white look worse. To me, in the photos the white already looks too stark. Maybe this color works in other rooms, but to me it looks too bright with the brown and black furniture. I also have reservations about how painting part of the wall (behind the console) a dark color would look IRL. I think it would look awkward. It's certainly not something commonly done. You usually only see it if the darker wall section includes a fireplace. If it were me, I would paint all the walls more of a color instead of the white. It doesn't have to be a color like green or blue, probably a neutral would be best.

entire wall. yes. it's too white as is.

try out some diff colors you like. I'd go darker.

Paint all of the walls with some color, get end tables with lamps, and turn off those overhead lights.

Beverly, like the suggestion for charcoal. I don't like 'dove gray' and similar cool grays, but the warmer charcoal looks nice. Agree need to get some lamps and endtables. The overhead lights have a 'nightlight' mode that we usually use, but turned them on bright for the photos. We've just finished removing a wall that previously divided this room, replacing flooring, etc. We have a family of 7, so need lots of seating :)

One option is to test it first with samples and see how it feels at different times of day. Sometimes what looks good in theory ends up feeling too strong once it’s on a full wall. As already said paint is at least easy to work with and is not so expensive.

You can place any ceiling light on a DIMMER.

It's easy to replace the ceiling lights with recessed lights which can then be placed on a dimmer.

I would paint it. My favorite brownish gray is Farrow & Ball’s ”Mole’s Breath”, have it in a few rooms in my house, it comes across a little more brownish than shown on the website. Sample pots available.

White walls are jarring and I suggest you repaint all the walls the same color. Choose a smoky green that work with both sofa colors.

Benjamin Moore looks like a good choice.

Would suggest the whole wall to be painted instead of just a portion like your mock up.

More inspro to go with wooden slat wall