I first heard about the Cidada principle on Sitepoint years ago: The Cicada Principle and Why It Matters to Web Designers. I was intrigued and I’ve tried using a couple of time to overlay background images to create the impression of randonmness. It’s very interesting and really nice to allow for some more organic variation, so I was quite pleased when it reared it’s head again:
nth-child is a nice way of applying this. Great stuff!