General rule, art should correspond/create a visible bond to what's underneath, so usually you go by hanging the art 6 t0 10 inches above what's below .

In some instances, lower works as well, but most times higher doesn't

I would say 5-6 inches above the sofa. Will the sofa be centered?

I’ve been going back and forth about centering the sofa given the end table and the chair (both of which look better on that side) and the coffee table. The rug (from my previous home) is a bit too small for the sofa and end table, but it will be a while before I get a new one. Opinions about that welcome as well.

The rug and the entertainment center on the opposite wall are centered.

Danielle, centered seems better to me but I'm not a pro. See what they say. I'm just thinking the art would look best centered on the wall over the sofa and between the windows/curtains. You also don't want the art too high. It's nice when art is about 2/3 to 3/4 the sofa's length. You mentioned curtains, so they can take up wall space, too...depending on what you choose.