Let's assume an insecure communication channel.
Alice makes a public key (we assume is PGP, but any asymmetric crypto could be used unless it doesn't have fingerprints for checking) and sends it to Bob.
Then, Alice sends to Bob a photo of her key's fingerprint so Bob can check if a MITM attack occurred replacing the key.
Obviously an attacker could replace the photo too, with the fingerprint of the eavesdropper's key, but, how likely would this happen? What about time? The eavesdropper doesn't have all the time to do it, and we assume that Bob immediately receives it, so is it safe to assume that the photo of Alice's key's fingerprint is good?
The same could be applied with hash checking, I'm I correct?
And what if Alice signs the photo with her handwriting before sending it? Let's say with a photo editor? I think this would make the eavesdropper taking more time, and Bob would surely know that something is wrong if the photo takes too long to arrive.