Either a green from the floral upholstery or a dark green could look great. Floor to ceiling.

White, they are trim, let the black mantle and bricks be the star. Where is the tv going? (Not over the mantle!)

TV stays on the right side. I lean toward the darkest green from upholstery.

I like the bead board on the back wall.

IMO unless you plan to eliminate a lot of the knickknacks and streamline I don't think you need shelves on both sides. I would do the FP part of the wall like the 2nd picture posted by Design Fan and have nothing on each side

I found this planner to be very helpful for my built-ins Check out the planner here

I like the idea of green built-ins. I show it with all glass fronts but you can have open sheving or cabinets doors - whatever works for you.

Consider mounting a framed tv above the mantle so when not in use you can switch to whatever artwork you like.

Here’s the cabinets extended to the ceiling with solid cabinets doors on the lower portion.