I would suggest end tables with lamps and dim the pot lights, or turn off completely as they are harsh. A comfy throw would be nice and a coffee table too. If by accent wall you mean a different paint color, I say, no. Never cared for that look.

Do all of the seats recline or just the two on the ends? If just the two, I'm wondering if you could get a small enough round coffee table that wouldn't interfere with the reclining seats. It would give you a place to land your drinks or a book, and it breaks up the black rug.

I would add draperies to your existing window treatments, and treat the three windows as all one window.

Add a large print that coordinates with the three you already have and add some greenery. Change up the pillows so they blend your colors a little better.

The bulbs in the ceiling downlights are the wrong color. Too cool. You're at about a 5-6 and should be at 3

IMO your were heading in the right direction with the area rug style, but It's a bit too black for the space. See how much for interesting the space becomes without that black 'hole' in the floor.

Art on the wall behind it.

Personally I don't like pillows on furniture that is pillowy looking. I would just do a throw as suggested in @Emily picture. Add art and window treatments also as in @Emily picture. The black rug is very high contrast and the black pillows are very dark.

No accent wall - coffee table + art + accent colors for throw/rug/different throw pillows. Add some texture with the throw + pillows + window coverings. Adding something in stone + a plant. All of the foregoing helps make a room look "cozier."

Emily has made a nice image already - so, I decided to make one to see what the room would look like if you replaced the existing rug with a new one.

I'm not sure why it put two pieces of art on the wall by the floor lamp (looks too busy) - I only wanted one! Also, I decided to try a floor lamp + move the plant out of the corner just so you could see something a bit different than what Emily posted.

What should be missing is all the black. The sectional is dominate. Consider using a rug in the same color. Throw pillows, that have a bit of the floor color in the mix. I like the Kravet print and the trim on these pillows from PB.