Here are some theories of mine. I'm not tied to these, please destroy them if you can... because they're infecting my brain.
The man who apparently financed the project according to the video: a younger Locke's father?
The woman in the photo with Desmond: Jack's wife? I don't understand how that could work... but that's what theories are for
The shark in the water: had the symbol on it, we know that. But the symbol is slightly different. There's no swan on it, just a straight line with a seeming bulge in it. What that means, I dunno. But there it is.
The book that there's a closeup of is titled "The Third Policeman." A search on Amazon turns
this up. (Interestingly enough, the third result in that search was the Girls Gone Wild: Extreme DVD...)
The driver of the SUV that hit the woman that will become Jack's wife had a time of death of 8:15. His last name was Rutherford, same as Shannon and (late) Boone, and we know that their father is dead... same guy?
By the way, Locke. I love you, man. You're cool. But a leap of faith does not mean do the safe thing. It means let the clock run out and see what the hell happens. Whatever is meant to happen, will happen. You're the one that's all about that kind of thing; be consistant, wouldja?