I just found a good comment that I'd written on rambly's blog in 2008:
http://rambly.wordpress.com/2008/08/26/thoughts-on-the-tiddlyzui/#comment-236
http://rambly.wordpress.com/2008/08/26/thoughts-on-the-tiddlyzui/#comment-236
My idea with the fractal background thing was to have a background that reveals progressively more detail as you zoom in, but the character (colour/texture etc) of the pattern changes too, so that you can tell instinctively whether you’ve woken up looking at a row of sand dunes or a row of mountains. Imagine something like a Gosper curve that gets rounder as you zoom in….