This kinda miss the big issue with identity. All this does prove is that at some point in time, the entity controlling the private key for a given address, was in possesion of that picture. That's it. I may post a picture of my coworker, that was carefully manipulated to seem like he was holding a piece of paper.

If you want true proof that a certain identity belongs to someone, you either have to meet with them physically and get the key, or trust a 3rd part to have done it for you. So far, everything else have fallen short, and this is not an exception.