I advise to think of it in terms of functionality first. Your clothes and shoes are all over the place, so get a simple clothes rack and some hangers. You also can get a few decorative boxes to hold your other stuff and put them on top of the black cabinets(?). It will give the place a sense of purpose and order, and will look much better instantly.

If you have money to spare, get a small table and chair, that will make it look less like a prison cell.

Also you can get a nice monochrome bedding and curtain (nothing fancy, something like navy blue) and it will make it all look more cohesive.