is that a recessed area for the TV?

I'd Mount the TV on the right side of the fireplace above the floor venting

you could get a larger screen. Center the TV on the patio door and table/lights.

Paint the dark wall the same color of the rest of the room. (or a color you love rather than the black/navy to complement your decor items)

move the two swivel chairs to the Alcove and create a vignette with your decor pieces. a table and lamp.

and face one sofa toward the TV, the other making an L shape and add a larger end table where they meet, add a table lamp or floor lamp...

Put the credenza behind the sofa and use it for Dining storage.

IF you think you need some color on the wall, paint the Wall to the right of the Fireplace a Dark Taupe color in the stone to unify the wall/TV backing.

move the mirror on the mantel to next to that single doorway.

I did just update the picture.

Some 3 dimensional creation would look great in the room centered under the downlights. You can spend a lot or a little.

Cozy basement! I love the armchairs and the fireplace is lovely too.

That empty wall has so many opportunities to shine for you.

1. Remove the factory pillows the sofa came with and either ditch them or replace them with fluffy down insert pillows in an accent color. Blue or light green could go well here.

2. Looks like you have space,move the armchairs a little out away from the rest of the set up and get an end table or side table if you have the space for it. If not, use the coffee table but keep it clutter-free.

3. Looks like you have also ample space behind the sofa against the wall. I see the radiator but I would highly suggest you can possibly put the sofas adjacent and the 2 armchairs on the radiator wall. It would create a nice walkway from the stairs ( as seen in your tv reflection) to the sitting area.

4. Swap out the sconces with something bulkier and possibly an accent metal like gold or wood.

Your plant also on the mantle looks outdated and dead b/c of the color of the ferns, so a richer green plant might look better.

As for that wall, a large canvas seems fitting here. Something calming with blues or greens. Otherwise, a large art piece of white wood or cream would look nice too. Not too much metals or dark colors because your space currently looks dark.