You can take large sections of fabric, starch them and hang them between dowels, kind of like Chinese scroll paintings. You could also paint huge canvases and hang them from the ceiling. I have seen clings designed for painted walls, but they are usually for children's rooms with rockets and ponies and the like.

my old roommate went to the art store and bought a bunch of canvases and paint. she painted each one herself with one color on each canvas. she hung them all up on our huge open wall and it looked pretty cool. no talent necessary and you can spice them up however you want. tapestries are another good idea. either way it just puts a few tiny holes in the walls that you can easily patch up yourself before you move out:)

"window coverings must be white"

So hang white pull-downs AND use tension rods to drape with bright stuff.

Lots of good ideas! Rayona, have you tried the fabric/starch idea? Was it difficult? Messy?

tapestries, old persian rugs, sarongs- you can hang just about anything from the walls...

though honestly, I've painted every apartment I've ever had. went looking for landlords who didn't squawk, ultimately...

three of them paid me, or kicked me back on the rent (since I was also doing things like repairing trim, fixing botched plaster jobs, and things like that) one got a bit carried away when he found out I'd stripped the 14 coats of paint from the oak stairs with the mahogany bannister, and had me paint the porch, the stairs, and the downstairs lady's kitchen...

one asked that I paint it white before I left, but paid for the paint. only one actually ever complained- and when I showed him the BEFORE pictures, he stopped nattering on about my security deposit.

but I LIKE big prints on the walls- and with the dowel/scroll idea, you can do 36" wide bands from floor to ceiling.

big drapes (even if you only paid a buck a yard for the fabric, and draped it over a curtain rod without even sewing a pocket) help, too.

I feel your pain. But first an idea. Go to a copy shop or somewhere similar and get them to blow up one of your favorite pictures, outdoor scenes, etc (i'm getting one of my favorite scene from breakfast at tiffany's to make it look like a movie screen.) My apartment at least has some kinda cream-colored walls so they're not white...but still drab. And on one random wall in my kitchen, some idiot decided to put this ugly floral wallpaper. The bathrooms are wallpapered two different shades of really weird green. What do these people do, sit down with a bunch of wallpaper books and their eyes blindfolded and say "I want...this one...this one...and...uhh...hmm...this one?" My mom is an interior decorator...i've got a year lease...I'm thinking about saying screw them all and painting the walls red. I'll paint em back...I promise.