Well, I guess I can start with my own thoughts.
If there's another website that we can use to do this, that would be great, but I'm not familiar with flickr, etc, so someone who's a pro with those sites can chime in.
Someone can post a thread here on the forums with a description of the contest, and a link to the submissions page. BSing, discussing, etc can be done here.
A page which includes the description of the contest. A form where you enter your name, forum nickname, title, and photo. It'll check to make sure you meet the requirements (ie. you have a title, a forum nickname, it's 800 px in any direction max, etc). It'll also end on time by itself, and automatically generate a voting page.
Multiple pages which makes it easier to vote. You enter by entering your forum name. You are shown a page of all photos. You give it a star value or a number 1-10 for each one. You can add additional comments about each photo as well. Essentially you'll rate each photo. At the end, it'll show you a tally of all votes up to that point (either average or sum to determine the winner). You can't view the # of votes each photo has gotten until after you vote. At the end of voting, a simple page showing the results publicly, with voters identified, and the comments for each photo displayed (can by anonymous if we want).
I dunno, that's kinda what I envision for the future. We can make it easy to submit new contests, etc. Maybe I'm over complicating things, but this is something a little php code with a mysql backend can easily solve.