Maybe they could use something like Chernoff faces (a method in which data is converted into images of a human face on the grounds that people are better at distinguishing faces than other images).
How much of a face would you recognize if it is rendered with ASCII on a console though? Which is probably the default use-case for SSH for 99% of people.
Heh... as someone with prosopagnosia, this wouldn't help too much. But I agree it'd help most people!!