We just updated a room similar to this. You could do some great tile work at the fireplace to make this room brighter. Also you could do some lighter shades as well. Good luck!

We tiled over our existing fireplace. Really made it look so different, as well as updated.

Nice ideas , new to this thanks :)

Since the ceiling is at an angle where is the best place to end the tile or go all the way to the ceiling ?

There are all sorts of things that come to mind. Take fireplace all the way up to the ceiling following the slant. Paint wall over the windows close to the color of the material you use on the chimney. Use a metal or slate or anything with a shine to reflect light. Use a light stacked stone for the fireplace is another choice to consider. Good luck.

If you stopped any treatment before reaching the ceiling, the natural stopping line would be the tops of the windows to the side. Then you would want to create a header/valance across the whole wall to tie everything together.