Make pendants, earrings, keyrings or whatever from them! Flags, little arworks, book covers, you can paint anything you like.
1
Start out with any old card that isn't valid anymore.
2
Cut it into four.
3
Round the edges, and pierce a small hole in one of the corners.
4
Now paint whatever you want, and when you're done, give them a coat of varnish or white glue. Put a jump ring through and you're done!