Aww, I think bias is the wrong word. Even if it's the right one, it's not an intentional one. Maybe perceived unfairness? It's not even on the posting side, it's on the voting side. I'll try to explain, but keep in mind I'm at work so can't devote a lot of time to doing so. Basically, when the voter (the public) is looking at the pictures in order, by the time they get to the last photo they likely already have three in their mind they are planning to vote on. This means the further down the list you are the better your picture has to be to knock off one of those three. It probably doesn't make a huge difference in the end, but in tight contests of one or two votes making the difference, it could be the decision maker.
I honestly hadn't even considered that some people might view the randomization as being handled unfairly. I see your point there. Maybe the listing order really is nothing more than a lose-lose situation regardless of how you do it.
Edit: Check out Tinsley's comment on this. She said it much better than me.
