When you say "what is missing", what you're really asking is "why doesn't this look good". And the reason it doesn't look good is not because of your blank walls, it's because your couch is backed into the corner. Move your couch into the room away from the walls, then decide what to put on the walls based on which direction your couch is now facing. Maybe it will be a book case of some kind. Maybe a console table with lamps. Maybe it will be a hanging TV. Maybe it will be art work. We don't know and can't offer any other advice because we can't see the rest of the room.

We will be getting colorful pillows/throws and new carpet. Way too much brown in this room. Painting the walls aren’t an option now. They all run together and we would have to paint everything

Can you center it on that wall? Yes, I know the window is there. What about the other wall for the bed?

I always admire @lisedv’s work. She gave a direct answer to your question and her mock-up above looks really nice. Here is an alternate idea - if you only have one large wall to decorate in the living room, not using large art there could be a missed opportunity to bring color, warmth, and personality into the space. Smaller family photos could go on a smaller wall in hallway, loft, master bedroom or . . .