The current wallpaper generator uses a mix of fractal information and random noise. The method works pretty much how I explained earlier, but with one important extra trick.
The result of each pattern render is a mixture of big, smooth (and antialiased!) shapes from fractal information and wacky complex shapes from random noise. There’s no way to know how much of each a render will contain until it’s finished, but it turns out that patterns with an even mixture of each type of data tend to look better to me. To help make this happen, each time a wallpaper is created, the generator creates ten random patterns and then picks the one that came out the closest to a 50/50 mix.
I’d still like to fiddle with tiling different shapes, and adjusting the target mixture to something less obvious could help, too. I’m pretty happy with it so far, though!