What would better generate visual randomness for cryptography than lava lamps? I find this solution interesting as there are patterns to other seemingly random things in nature. For example, no ocean wave is ever going to be exactly the same, but they do follow a pattern of the tides. From a crytography perspective, how would a high resolution video of something like a beach compare as a solution?
Tenish years ago I wrote a pseudorandom number generator from webcam stills. Since I wrote the code in the middle of a midwestern winter, my first solution was a shot of the outside; falling snow. When the snow started to slow down, I moved to using a lava lamp. So to answer your question...falling snow works really well juxtaposed against clouds.