Too bad about the location of that beam. You really need larger art but it is in the way. Try putting a wood mantel on the FP. The current one is more of a ledge and looks too narrow to hold much of anything. Art should hang 5" above the mantel and be no wider than the firebox opening if that guideline helps. Try the art from photo #2 instead of the lighter one. What you're using right now for mantel decor doesn't have the right visual weight to handle the "heaviness" of the stone and the beams. Another general issue is that the windows appear to be low, mostly due to them nearly bumping the ceiling or beams. Lowering all art so it is centered 5' above the floor should help. Large pieces of furniture like the cabinet left of the FP should be placed on your higher walls to give a feeling of spaciousness rather than the current cramped feeling. It seems like we've landed in a hobbit house on that left side of the FP since the ceiling is so low and the furniture pieces so big. Cornering furniture is another problem. Can the TV be moved to the cabinet's location and placed flat against the wall? That way it and the FP become one focal unit.

can you get a nice wood beam mantel like some of these pics?

I love your green painting but would look better if it was displayed on the mantel like this one. Hanging it doesn't work because of the low ceiling height there.

try doing the art on one side and take the antlers out (maybe spray them white. I did it to mine and it looks really nice) and sit those on the left side like in the first pic. If you could find a mantel in the wood like that, I think it would look fab w/your decor.