A company named Klutz makes arts and crafts sets for kids. They made one with shrinky dinks and that was the first time I'd seen the stuff in decades. Last Xmas I found beautiful ornaments made by using the same plastic film. Now I see it in jewelry, magnets, hanging from window hooks, etc. My local art supply store has the standard clear and opaque, but it also has colors. You can even buy some shrink films that are safe to run through an ink jet printer.
The idea, for those who are unfamiliar with the process, is the following. You trace (or make your own sketch) on the plastic. Then you cut the shape out and pop it in a toaster oven. It curls and shrinks and flattens out, leaving you with a harder, smaller version of your original design.
If using an in jet, your options are limitless (you can use photos!)
Here's an example from an online source: