So far, I have used images as the color basis for designs that are build up from predefined polygon tile shapes. Recently I have started to re-create simplified versions of the original images. By merging neighbouring tiles that approximately have the same color, more complicated and irregular polygon tiles are made. This brings the design closer to the original image, and at the same time randomizes the tile shapes.
The degree of randomization can be controlled by playing around with the size and shape of the original tiles, and with the maximum color difference allowed for tiles to merge. The current 'incomplete' implementation of the tile merging even creates an additional random effect, shown by irregular lines present in some of the polygon tiles. In a way, this approach is a crude attempt to vectorize a color image.