Here's a quirky website. I don't remember how I found it, but at Off the Map, you can make an imaginary place. First choose a virtual backyard. "Then scavenge through some 'junk drawers' to find 'objects of delight' that you can use to create your own visionary world." You can also browse other people's worlds or email yours as a postcard to your friends. (Or maybe you won't want to tell anyone you wasted that much time.) I gave it a try. Here's my animal school yard, created one night when I was up WAY TOO LATE.