http://en.m.wikipedia.org/wiki/Identicon

https://es.gravatar.com/site/implement/images/

http://blog.gravatar.com/2008/04/22/identicons-monsterids-and-wavatars-oh-my/

http://www.splitbrain.org/blog/2007-01/20_monsterid_as_gravatar_fallback

http://www.splitbrain.org/projects/monsterid

(On the last page, try to refresh/reload it and see what happens to the monster.)

We are currently using Identicons. So, what if we manage to make something similar but using the Machines' "faces" instead? They could have different amounts of eyes and antennae, different colours, and different positions (facing in different directions).
This could make the forum even more unique!