Whether it is vision or words, the point is to enlist some of our primal, automatic brain machinery. Both the random word lists and randomart are a good start, but far from perfect.
The word lists ignore and even foil, our gramatical machinery. And I at least have never been able to remember what my own randomart SSH key fingerprint looked like. Adding colour might be a good start.
It has to be a visualization in which changing a few pixels make it look significantly different. Otherwise we can still make a 'low distance' brute force attack.
What you need is a picture that makes the visually salient information tot up to about 160 bits.
That's tough, but since the human visual system is so powerful, it's not hopeless. But we would need real psychologists to help design the art generators, backing the results with experiments.
http://superuser.com/questions/22535/what-is-randomart-produ...