Superpowers assets background elements
Background elements from Sparklin Labs' Superpowers HTML5 game maker.
Superpowers has a variety of free assets: 2D sprites, backgrounds, 3D models, sound effects, music, and animations. This is just the background elements, but I'll be uploading the other assets: http://opengameart.org/content/superpowers-asset-packs
They make periodic updates to thier asset packs. You can always find the latest version of the full asset pack at https://github.com/sparklinlabs/superpowers-asset-packs