[shagie]

The sunset pattern are... even less distinctive.

Aside from identicons (which I think work rather well), I believe that a large Mondrian style image with a random circle on it that is then rotated, and scaled to the appropriate size (and cropped if constrained to a rectangle).

This allows for an image that attempts to avoids problem with color vision.

The issue that I had with the Boring Avatars is that too many of them were the same. Switching to ring or sunset had many identical ones. The Bauhaus version had a limited pallet so that the same three colors occurred frequently and only distinctions were in orientations of objects which weren't that distinctive themselves.

The amount of uniqueness per image in this is rather low. The solid color and letter you mentioned has more easy to identify uniqueness.