I made backgrounds, but now I can't import them!

First thing to check is that your background images are saved as 320x200 24-bit or 8-bit BMP files. When you try to import backgrounds, only images that fit those parameters will work.

If you know your BMP is 320x200 24-bit (or 8-bit), and it still wont show up in the import browser, then the file's header is probably corrupt or wrong. Load it into a different paint program from the one you created it in, and resave it.