I've always enjoyed creating analogies like to see why certain behaviors, mindsets, and tactics are okay in some industries and others not. To wet your palette a bit more here's a wonderful essay analogizing math education to music (Famously, The Mathematician's Lament) http://www.maa.org/devlin/LockhartsLament.pdf
I tried a few really obvious backgrounds (Even a mario background for fun) and found a soft subtle background gave the best effect, although it looks like I went too far. It looked fine on the few screens I demo'd it on, but I'll update with a higher contrast background soon.
Your suggestion for the CSS3 is great, I'll definitely toy around with it in the next few days.
Secondly, Parallax.js can already do this. It simply moves around the divs you feed it, which can be tiny or full screened! This allows you to throw your own header on the top, or, if you like, a same parallaxing div in the center of your page.
And a TED Talk comparing the use of patents and trademarks in the fashion industry to software. http://www.ted.com/talks/johanna_blakley_lessons_from_fashio...
Both are quite insightful, and I think you'll enjoy them.