How it works

Adjusted image size:

Superpixel: 16x16

Reduced image

8-color palette from reduced image

Using the median cut approach explained here

8-color palette applied to reduced image at original size

Superpixels from original image sorted by complexity (data URL string length / number of pixels) shown here at 2x

Idea for using compression as a proxy for complexity from this suggestion by Arthur-1 on StackOverflow