I would leave the wall blank for now. It doesn't look like there is space for a sideboard, and a large piece of art will compete with the fireplace/tv. Instead, I'd add a rug to the room for some texture and color, add textiles (pillows/throw), and then re-evaluate. If possible, I'd actually move the tv to the stairway wall and add art over the fireplace.

I would hang a very large piece of art and forego the sideboard. Here is what we did with the wall that's adjacent to the fireplace and tv:

It seems like an awkward place for a sideboard so close to the doorway. A typical sideboard would be at least 18 inches deep and your doorway is maybe 30 inches. If your art is large, and your sideboard is 1/3 wider than your art, I don't see how that won't crimp the pathway to the door.

Would you consider art without anything under it? Could be fabulous with a really big piece of art. Or you could look for a shallower console table, 10 or 12 inches deep.

Agree with above. The sideboard will block the doorway.

A narrow console or bench may work better.