I know this is off topic, but still an idea that has interesting possibilities.

A team at Rice university is working on batteries that can be painted on any surface.  In one test, they painted batteries on some floor tiles.  In another they painted one on a beer mug.

Here's a link to the story.  In the story there's a link to a video explaining the process and showing the batteries.

http://www.theregister.co.uk/2012/06/29/paintable_battery_texas/