If this has been posted before, point it out and I will organise for this thread to be merged or dropped.

This is a post about the cicada principal being applied to background images.

I will quote from the blog to stimullate your interest and then provide a link so you can read first hand of the details -
depending on the species, every 7, 13, or 17 years these periodical cicadas simultaneously emerge en masse, transform into noisy, flying creatures, find a mate, and die not long after.

While this is a rather rock’n’roll ending for our nerdy cicada, it raises an obvious question: Is it just by chance that they adopted 7, 11, or 13-​​year life cycles, or are those numbers somehow special?

As it turns out, these numbers have something in common. They’re all prime numbers—numbers that can only be divided by themselves and 1 (that is,1, 2, 3, 5, 7, 11, 13, 17, 19, 23, and so on).

But why does that matter?

Research has shown that the population of creatures that eat cicadas — typically birds, spiders, wasps, fish and snakes — often have shorter 2 – 6 year cycles of boom and bust.

So, if our cicadas were to emerge, say, every 12 years, any predator that works in either 2, 3, 4 or 6 year cycles would be able to synchronize their boom years with this regular cicada feast. In fact, they’d probably name a public holiday after it called Cicada Day.

That’s not much fun if you’re a cicada.

On the other hand, if a brood of 17-​​year cicadas was unlucky enough to emerge during a bumper 3-​​year wasp season, it will be 51 years before that event occurs again. In the intervening years, our cicadas can happily emerge in their tens of thousands, completely overwhelm the local predator population, and be mostly left in peace.
Based on the above a designer has come up with a way of making backgrounds using a number of small images, where it is very difficult to see any signs of tiling.

Take a look at this example of a background. Expand your browser window to fit on screen. There are 8 images involved to make that seemingly non-repreating BG and the total image size is 133.8kb.

Here is a link to the blog topic that has the above quote.

Here is a link to a gallery of user submitted images based on the Cicada principal.