To prevent a similar-looking-fingerprint attack, you could just re-hash the fingerprint with a secret salt before displaying. I wonder if XOR'ing the fingerprint against a plain hash of itself could also be difficult enough?
Secret salt would have to be the same everywhere. So it has no sense to think about it. Just a good hash is needed, hard enough not to be brute forced, like scrypt.
Scrypt would probably be fine, though the addition of a secret salt (wouldn't need entropy, just secrecy) would be much better. On reflection, XOR would be stupid bad :B
For the more general case of analyzing binary data, I could see something like this being useful for other tasks such as visualizing network traffic, or analyzing logs. Basically finding some way to transform the data into an optimal form for human pattern recognition.
However another danger is all the emoji that look too similar. It can be too easy to forge one emoji wink instead of another. So it can be not so good an idea in general. But maybe somebody demonstrates the easyness of differentiation or manages to select only the symbols that are visually and cognitively different enough for the "alphabet." Still I suggest significantly more than 256 elements, and significantly different one from another. That's the hardest part.