Very nice room. A few thoughts...

Start with a nice large area rug or dramatic painting you like and pick colors from it for your furniture and decor.

Raise (and replace?) the ceiling fan to well above the lowest beam and use an arc floor lamp for light over the seating area.

Refinish the FP brick to blend with the stone.

The built-ins and mantel a light tone...Nothing similar color to the beams, they stand alone.

Paint the walls and ceiling the same shade of white.

Paint the interior of arched niche an accent color.

Complete the shell of the room and then furnish and accessorize, your furniture arrangement is fine.