I've had my eye on buying some wall clings for a long time now. Since we rent, and there's no telling when we'll get stationed somewhere halfway around the world, mine is the frustration of not putting too much effort into our house. So I try to channel my efforts to the spaces inside the house. These little suckers are perfect.
Etsy is teaming with them. The vendor who make these is Michelle Christina. I want to get the paper airplanes.
And then there's blik, which features clings inspired by Nintendo and Threadless. You can set up your apartment to look like an entire level from Super Mario Bros. Check it out.