Since decorating a rented apartment can be a challenge (with painting restrictions, etc.), wall decals are a great non-permanent way to decorate.
We admit, just because it's DIY doesn't mean it's green. As far as greenness goes, you might be better off with Fabric Wall Decals. However, if you have some left over contact paper, or some that just won't be used otherwise, this is a great way to use it up.
Instructables author Britsteiner has put together a handy how-to on making your own Vinyl Wall Art from nothing more than ConTact paper, tape, scissors and scrap paper. Her method, in summary, is to make a paper template, trace the design onto ConTact paper, and then apply to your surface. She's got plenty of tips on how to do it right so check them out at Instructables.
All photos used with permission from Instructables user Brit Steiner.