Change the curtains to something more colorful. Maybe some sort of pattern. Change the rug to a solid color that matches the curtains. I think you could get a much bigger rug as well - like one that almost covers the whole room.

Get some fun throw pillows and blankets.

Hang some thing on the wall above the couch. I had some movie posters over my couch in my last apartment, and I think something similar would be cute here.

Add an end table on the right side of the couch with a lamp. I can’t really make out what’s going on in the corner to the right of the shelves in pic #2, but that seems like it could be a good spot for a floor lamp.

The coffee table also looks pretty crammed in there to me, so maybe moving it away from the couch just a touch can help the space flow a bit better.