You do have a very good point there, even if Lockes vision does actually come true as in it shows them getting off the island it hasn't happened yet so they cant possibly have a picture of it. Ben must have been off the island at some point.

Unless, what if Micheal took the picture at some point and has spilled the beans on Ben and thats how they got the picture, probably just rambling now but the thought just popped into my head while i was typing lol.