Hey Craig,
I'm definitely no authority on this, but I think the highest figure a single unsigned vintage photograph has reached may have been the almost-$90,000 for the ginormous Addie Joss benefit game panoramic from 1911. Here's a link to Heritage's 2005 auction:
http://sports.ha.com/c/item.zx?saleN...No=19707#Photo
I had forgotten about this one, even when the Joe Jackson Conlon photo hit its final number of $32,588 (and I think that was without the juice?).
They're definitely been a lot of other contenders for high figures, including that Horner Wagner photo from the Sotheby's auction. I feel like a LOT of the other five figure prices reached for photos have been for Conlons, be they Mastro's Ted Williams portrait or some of the shots of Gehrig's and Ruth's eye closeups. And, they're also those wonderful early 1920s Paul Thompson shots of Ruth, also from Mastro's collection, which I think ranged from 10k to 18k.
Granted, Jimmy, Ben, Lance and the others could probably chime in with better researched info...
Graig