I am getting asked this over email a lot, so I will post it here. The background image I am currently using for my theme (which is below, in case I change it later) came from a picture I took of a concert. It was the Crystal Castles show at Austin City Limits 2012. It was a fantastic show. I highly recommend checking out Crystal Castles if you like crazy electronic music.
A couple people put some YouTube videos of the show here.