Paint or cover them with colorful paper. What are you using the cans for?
Lots of ways: Paints, make mosaics, paint by number kits, making Clocks. Those are just a few ideas to get you started.
How To Etch Aluminum
wrap rope around it would be nice
I flattened mine and painted with alcohol inks. Then I cut them into butterflies and flowers. You can wire them up and hang them.