A set of geometric prints would be a clean non-cluttered look.

I'd keep the plant and lose all the little stuff on top of the file cabinet. I'd leave the computer wall free, and put a single framed print on the wall to the left.

Keep the plant; prune it back so it fits the space better. Rustic shelving, three shelves above desk. Bring the blue into the other side of the room with accents. Paint file cabinet black (with spray paint) and paint white bookcase black.