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/