Here’s a set of preview from the Illuminati abstract background set. They’re watermarked low-res 600×600 images. The package which is now on sale at GraphicRiver.net contains 3 layered PSD files for 3 abstract backgrounds included in this set (which I call Ocean, Limbo and Hoops) which you could easily customize. Each have 3000×3000 resolution. Changing colors is as easy as unhiding a layer!
Click on the thumbnail to view the larger image.