Here is a cool tutorial I found for making abstract backgrounds. They primarily use particles in blender. https://www.youtube.com/watch?v=J2G5Y1Ezy8g
Particles has great potential when it comes to making abstract art, and they're incredibly fun to use. They are also a great tool to know for 3d art in general (starfields, dust particles, rain ,grass/hair, etc.)
This tutorial also includes some basic animation, and will show you how to use text, particle effects, basic lighting and a little physics to achieve a small intro movie. While it's not exactly what you're looking for, it will introduce you to various tools that will help you make better backgrounds. Heck you might even like to start making some intro movies yourself.
Also follow the links to the related videos for more of the same. I think once you've got lighting and the above mentioned tools down you'll be on your way to making some great backgrounds OP.
I'll be looking forward to see how you progress OP. So be sure to come back and show us what you've come up with.