Move the desk to a different location, or purchase black files to fill the space and boost file unit/s to desk top height exactly, with a base you make and paint black., Remove the standing lamp, get a desk lamp. Remove clutter, and plastic garbage bag liner. Its a trash can, not a garbage can : )

Or get a new desk that fills the space.

Will it fit on a side wall with chair in the space?

How about turning it around with the chair against the wall so you are facing forward?

Jan's suggestions are right and I would add a sconce on either side of a painting that is installed lower. Don't be afraid if the computer is visually overlapping the picture behind it. Also, paint the back wall an accent color you like to give the space more presence. Ditch the floor lamp and definitely don't do another floor lamp.

Cord management too. Good luck!

I would remove the floor lamp and place one on the desk. Then just relook at how you have decorated the wall...larger art or create a collage - something more interesting to look at. You could also add floating shelves for practicality, but also would be a more interesting look. Use chalkboard paint and have fun with the wall. Don't forget to add a great chair that adds to the space. Suggest looking on Pinterest for tiny offices and there are so many inspiration pictures that would help. Don't face a boring wall and there is no issue with desk not being larger. You could even move it into the corner and add a nice piece of furniture for storage.

Thanks everyone!

Here are a few images of a home office we did for one of our clients. It might help you move forward to see it. Notice the balance?