That would be too dark next to the stone around the fireplace. If you want to change the color of that wall, choose a color from the stone, but I think it looks good painted the same color as the other walls. Every room doesn't need an accent wall, plus it is already an accent with the shiplap. Your mantel looks a little cluttered, and although I like the picture over the fireplace, it doesn't complement the stone very well and looks a little too large.

a softer black, and flat sheen. Yes the art above the fireplace is too big, do you need framed art there, your simple stoneware jug and twig is nice.

Bring the furniture into the room a bit, away from the walls... at least front legs of all the furniture ON the rug.

The art is a frame tv w a pic of our lake out front. We change it frequently.

Not black. Either the gray of the other walls, or one or two down on the paint strip. Do a semi-gloss finish on the paneled wall. It isn't ship lap and neither are the paneled walls that Joanna Gaines installs.

Having black as an accent can work really well in some spaces. However, your current set up looks good as is, so we wouldn't recommend painting the shiplap black. Here are some of the accent walls and fireplaces we have done for our clients so you can see how we worked it into the designs.

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You mean paneled because it is not ship lap. If you nail plain wooden boards to a wall and call it shiplap, that's not quite accurate. There are long wooden boards involved, but genuine shiplap actually has overlapping grooves that fit together to make the design weather-tight. You can identify shiplap by the overlapping "rabbets," or grooves, in each board.

Paint it the dark gray of the chairs.

The shiplap is fine, it’s the art/pictures placement and the brown fan that throw things off. Please post more pics of the room, and replace the brown fan with a white one that blends in better. Nice room!!