I just moved and was looking for things to put on my empty white walls and found blik wall graphics, stick-on decals that are much much easier than that whole stenciling business. The decals are fully removable so you don't leave any residue on the walls and you can easily switch from space invaders to flying birds.

About those birds- I was just reading about how millions of birds die every year as they head back north for the warm months, many of them from crashing into clear glass windows. If you put something big and colorful like these blik decals on your windows, you can help them navigate around the glass. Keeping the lights off behind windows at night will help the birds too, as they won't be tricked into thinking they are heading into a safe space inside.

Blik also makes decals for decorating everything from drinking glasses to cell phones.

Wall graphics packages range from $35-$50 at blik.