Do you limit the number of photos? Seems like if the number of photos in the pool far exceeds the number of votes coming in, each photo would only ever have a handful of battles. I've build a similar voting system before but the purpose was to find a winner amongst all entries.
hey daniel, long time no see! we're probably going to cull the pics and delete the ones that fall below a certain elo/win/loss threshhold, so it should keep the quality of the pics high. and we can adjust the threshhold so that it keeps the total number of pics from getting too huge.
