Could the Tetradic color pattern be expanded to allow /dev/random be "pretty" for cryptographic key purposes?
It depends on how you define “pretty”, but there’s plenty of possibilities. Assembling a grid of shapes as in Identicons would be one example; using the numbers for coordinates and zoom levels on a fractal like the Julia set would be another. Our eyes aren’t good at measuring absolute values of anything—perception is heavily dependent on context and lighting, cf. the dress—so you probably shouldn’t rely on color alone as the identifying factor.