Abstract geometric identicons like my original implementation as well as variations used at Wordpress and StackOverflow are, while nearly impossible to remember, distinguishable in a pile which comes in handy when distinguishing the 'voice' of individuals in a long thread of comments.
To use identicons as permanent identity, one has to 'identify' with their identicon. We can identify faces of our friends because we shared memories with them, stories if you will.
So robotic identicons like yours can be made more memorable if users had some ways to create a story they can associate with it like 'blue viking with left arm missing', etc.
But I like the idea. Perhaps the image problem could be met by combining it with a bio (giving a story); and the "make sense" problem could be addressed by a story grammar (following the hero's myth as a template, with recursive and optional parts), written using templates consisting of canned pseudo-english sentences with gaps filled by a set of names, objects, places that play the various roles in the "hero grammar": the key, the sword, the grail, the shadow, the mentor, the ordinary world, the special word, various thresholds - perhaps some word generation for place names. If the story made sense, as a journey, it might be memorable, even stirring in an awkward way, despite all the grammar/template/presets...
Of course, maybe I'm wrong: "<color> <warriortype> with <injury>" is already fairly rich. Even, extending it to incongruous occupations (surgeon, nurse, motorcyclist, developer). Perhaps, like theatresports, just starting points of a place, occupation and problem is enough to suggest a story to the user?
Everywhere we look in RL, there are stories being told all the time.
I think an interesting way to apply identicon to certs is to map each cert attributes to an 'attribute' of identicon, visualizing attributes.