Pic Factor is one of the most controversial of the many "factors" that have been discovered (invented?) by the Gurus who reside in Board 8's Stats Topics. Some claim that pic factor does not exist in matchups between well-known characters, because users will vote for who they like more, regardless of the Match Pics. Others, however, attribute many results to pic factor, such as Bowser's overperformance on Snake, Snake's overperformance on Sora, and even Link's 2003 defeat at the hands of Cloud (because of his "Celda" design).
Some variations on pic factor include The Jug Factor, which claims to explain why attractive females overperform on males, and the Solid Shit Factor, which would explain why Snake performs like "crap" every time his NES sprite is dragged out. Pic factor appears to have been validated at least somewhat by several strong showings turned in by 'Face CATS,' who is considerably more recognizable as "that guy from the flash cartoon" than the so-called 'Eggplant CATS' who did so poorly in earlier Contests.
Big Boss became the poster boy of pic factor in the Summer 2007 Contest. Many expected Magus to advance into the 2nd round, but a combination of Magus's unexpected weakness and the debut of the feared "Naked Snake" pic helped Big Boss advance easily.
In the 2008 contest he went above and beyond, when the best picture he could ever hope to get transformed him into Solid Snake strength-wise. In fact, Big Boss is nearly equal to Solid Snake in the raw stats.
The 2013 contest might have confirmed the existence of this factor with the match Mewtwo vs Phoenix Wright vs Vincent Valentine. where Vincent got an obscure DoC picture instead of his usual appearance (to the point where it was called sabotage). While it's likely Mewtwo would have won easily anyways, Phoenix Wright would never have been able to put those results against "normal" Vincent.
During Character Battle X, Ulti made a series of polls asking about pic factor in various locations -- Board 8, Poll of the Day, Reddit, and Twitter. In all of the polls, it was found that 35-40% of people are influenced in some way by the picture when they vote (the polls were simple yes/no polls). Ulti was very surprised by this and had always assumed pictures did not matter at all in voting.