There are lots of cool DIY ways to cover air vents attractively. You could make one that covers the entire vent-attic unit and it would look like an art piece.

I’d at least remove the mirror on the left. It will fight with what you do on the vent wall. Then a piece of art over the vent that is held a few inches off the wall for air flow. I’ve seen vents painted to look like art but they still look like a vent. At the very least paint to match wall. This is a awkward situation.

This is too small for that spot, use it for inspiration,

I would paint all one color and then put a decorative grate on top to minimize what you have going on.

It will be easy to take off and allows air flow.

Decorative Cast Iron Register, Without Holes, 10"x8" · More Info

Thank you for your suggestion. I thought about that too but not sure it will look right with only half of the grate being the air return.

Idecor54 thanks for the insight about the mirror. But I don’t want that wall to be left empty. Maybe word art or family photos.

Lindsey that’s a great idea. I’ll start shopping for a grate.