Hi. It would help to have more views, to see the rest of the room, but my initial reaction -- if the desk in the corner can't be moved, would be to place a fairly large piece of art on the wall (unframed canvas would work best -- this work is by Monet), use some sort of neatening conduit for the wire, and remove all or most of the items on top of the desk. It would be great if you could put an original piece of art there, but just please your own taste. All manner of art styles would look good in this room.

You would have more options, I think, if you could move the desk, but as it is I think shelves or furniture there would simply make the wall look crowded.

Wall decals are a nice accent to a room, and will fill the void of space. Also there are many options to choose from. You can find them on Amazon or Etsy