1. Reposition your bed.
2. Rearrange your artwork.
Or change the framing of the art hung on your walls.
3. Cover your walls with tapestries.
4. Get rid of furniture you don't need.
Opt for smaller things that have multiple functions, like a desk that also functions as a nightstand.
5. Hide your cords and disguise your router.
6. Get actual curtains or hang your current curtains higher.
See different styling options as well as solid curtain choices here.
7. Donate your clothes to clear up space in your closet or dresser.
8. Add some patterned wallpaper or color accents to your door and other furniture.
9. Seriously tackle organizing all your scattered documents.
First, transition to electronic paperwork if you can. As for the rest, make a super nice and organized scrapbook or binder. It's like first day of high school all over again. See more details here.
10. Dust off all the surfaces and clean your electronics.
11. Mount more of your furniture onto the walls.
This includes lamps, bookshelves, jewelry holders (canvas), pictures, etc.
12. Pack up your non-seasonal stuff.
13. Get new sheets but more importantly, actually wash your sheets.
14. Go all out on pillow bedecking.
15. Change up the lighting in the room.
Try replacing your lamp, throw in some string lights (copper adds a unique touch), add a suspending lantern or bulb, or maybe even throw in a quirky chandelier.