There should be a panel of people who vote on the pictures, not everyone, and commit to making damn sure that there is plenty of variety. And no one else knows what makes it until the things are made and sent out. Then we have some mystery to look foreword to.
Hell, you can add 2 pages in the back with smaller pictures of runner up photos.
There should be a good mix of vintage, modern, colorful, topre, ergo dox etc. and I don't think a normal voting system will yield those results. Unless of course you vote by category. Best ergo dox, best vomit board, best topre, best novelty type board (full metal pokers etc.), best model M, best Korean custom, and so on