You could put some trim on it or paint the backs.

Simplify it. Remove small things. Add greenery. OR have a TV room elsewhere and turn that TV wall into a solid wall. Add art. There are two focal points at the moment.

The current mantel style will not work with the stacked stone. How far out are you taking the stone? I would remove altogether, that will also help in not having another horizontal line competing with the built in.

That ginormous TV simply dominates the room! And the fireplace clashes for eye dominance. If TV has to stay, I would remove mantle and paint entire fireplace same color as your walls (like second photo posted as inspiration). Maybe a warm white. Don’t think stacked stone will work in this room.....pick one focal point. Two are too confusing to the eye.

Unfortunately the ginormous TV needs to stay. This is a TV room next to a bar and billiard room. I like the idea of removing the mantel altogether. My plan was to have the entire angled wall stacked stone from floor to ceiling, and possibly adding the same stone behind the bar area.