Put lots of band posters on your wall or just general stuff you like. I have two dream catchers hanging on my wall over my bed and some cheap fairy lights by my bedside table. Ive brought some cute black rugs i have on my floor next to my bed and some sugar candy skull ornaments everywhere. I also add some candles and some incense candles.

Hang posters. Stick luminous stuff on the ceiling so that you can see it after lights out. Buy a clock that projects on the wall or ceiling. See link.

Put up a lot of nirvana posters

Hi I'm 17. My room is not too big and located on the attic. Two walls are grey and the other two are dark blue.I can't paint the walls. The furniture is white and that is a single bed, table, desk and a chair, board and a small shelf on the wall. I also have a green armchair and small carpet in the same color. My room has only one, medium window.