I would move the pictures to one side ( and down about two to three inches) and put up a couple of shelves on the other.

Do you spend a fair amount of time at the desk? If you do, I would get a good chair. Mine is from the Container Store. No cheap, but worth it. It comes in colors. https://www.containerstore.com/s/black-flat-bungee-office-chair-with-arms/d?productId=10028229&q=office%20chair

I would place plank shelving all the way across that wall, all the way up to the ceiling (you can purchase these in long lengths fully laminated in white (if that works) at Home Depot or choose other planking. Have good spacing so tall items can also be on them. Start your measurement above the desk top area so you have plenty of height below it for an open laptop and work area. You could possibly have space for 3 shelves. Some items could be in boxes, some items could be simply decorative.

Planks are what I showed. They can be cut to measure. The chair is great. I've had mine for several years. My sister liked it so much she got one too.