One of the interests of Alan Turing (1912-1954) was pattern formation, for example, how do leopards get their spots? He proposed a set of reaction-diffusion equations, which can produce these patterns, depending on the input parameters.
A simple implementation can be made by taking an initial random distribution of "pigment", and applying two gaussian blurs of different radii, subtracting them, applying a limiter, and use this to update the distribution.
This repository contains a Python implentation, which can also take an input image to work on.