Great idea snuci, it's just a little easier to determine the eligible photos if you (roughly) go by year.
Khers has impressively proven that there is a lot of photo material posted on DT to fill such a category multiple times. I would like to pick up your idea but propse a quarterly or monthly contest so that you can basically nominate great photos as you find them since there is always a competition going on. Only the winners (top 3) or the monthly (quarterly) contests are then candidated for the annual award with all the popular prices. This will be a little bit like a keyboard-of-the-month contest I guess but with a greater focus on the artistry of the photo taken.