So I coded it. It didn't take long to write. You can see the end result on this page; look carefully at the background. Stars will fade into and out of existence slowly over time. Code is here if you want to take a look (it uses Prototype library, but would be easily portable to other libs). The end result is too performance intensive to use throughout the site (we're talking thousands of tiny HTML divs having their opacity properties animated continuously), but was a satisfying experiment, and shall live on through this page.