If you have bare walls, the new Pixels.com app will change that -- for a moment, anyway. The official app of Pixels.com is first and foremost designed to get you to buy artwork for your living space, but its coolest feature -- an augmented reality tool that shows what various art would look like on your own wall -- is actually a lot of fun to just play around with.
Before viewing a virtual canvas on your walls you need to print out a sheet of paper with a special symbol and tape it to your wall. Using your iPad's camera, the app uses that sheet to automatically resize and position a 3D version of the chosen artwork on your own wall.
I should note that the app is actually really great at identifying where to place the virtual art, based on the printout. In fact, since I just got done moving into a new apartment and have no idea where exactly my printer is, I traced the symbol from my MacBook screen onto a piece of paper and the app recognized it perfectly.
You can customize whatever painting or photo you choose by tweaking its size, frame, and other options, and if you end up falling in love with what you've discovered, you can order it right from the app. The app is free, and available now.