I would pick a color in the stone and change the color to bring that color out more.

there is also no clear stopping points on the side edges, unless you repaint the charcoal to the left wall. if you don't include the doorways to the corners, all you are doing is highlighting that the fireplace isnt centered on the wall.

i do think the charcoal is handsome, i hope you have some of the paint left to repaint the left corner. and the white heating vent.

I think it would look better the same color as the rest of the room.

I think all white. I know those paint lines would drive me batty. I do love the charcoal however.

If you use @valerieroman's picture for inspiration, you can paint the charcoal color on just the section of the wall that has the fireplace. Use the right side of the door frame to the left as one side, and paint the right side the same amount (so the fireplace is centered in the dark area).

I love the dark to bring out the stone, but think you should keep the dark color to the fireplace wall, not around the door frames. I would pick a point below the curve to stop the grey. I think the asymmetry is a plus. Consider hanging several smaller photos to the right of the fireplace in a vertical arrangement.