Here's another neat example I whipped up: http://tinyurl.com/y92b9o3 (URL shortener used since the actual link is 761 characters long, containing the entire texture source). It renders a Sierpinski triangle by doing x & y != 0, then mirrors it to the bottom-right corner (so as to cover the entire texture). It's a good example of the simple sort of math you can play around with, then immediately apply to a demo. Converting that to C to make it work in my demo consists of nothing more than replacing 'var' with 'int', which makes my life easy.

The post says it's likely to only work in Chrome, but I got a look at the default "brushed aluminium" texture using Firefox 3.6, on Win32.

Arg, meant to update that. Apparently it works in Safari and Firefox as well, but I'm not sure on which versions will work. Gonna go edit now, thanks.