Reuse

There's a tree in city hall decorated entirely in reused items. Here are a few of the ideas that appeared on the tree.

This one appears to be made from Christmas cards! You could either use ones you received in previous years, or ones that people have leftover and don't want to use. With a little creativity, you could probably do something very similar with old magazines, possibly using some stiffer paper as a backing.

This fun ornament is a painted lightbulb. What a great way to reuse those burned out bulbs!

This guy was some sort of aluminium can in his first life, and now he's an angel! (I cut off the wings a bit in the picture, I wasn't at a great angle.) Make sure to rinse the can out well before doing this.