My family is into cycling, A LOT! We live next to the Minuteman Bikepath, the busiest bike path in the USA. We use part of our basement as our cyclery (or bike boudoir). And it looked like a dungeon down there!
So we decided to spruce up the basement with some floor paint, and a mural.
You need some stuff:
1) Some art - your own original or a poster perhaps
2) An overhead transparency projector - or a modern PC projector
3) Some paint (latex house paint is fine), you can scrounge from your paint stash or buy small inexpensive samples at the hardware store.