I have tried to post on our Photo-a-day and I really think this area have to be made better. Take a look at how it is done on DpReview for starters. We have a mixture of topics, picture size and comments and they are at time completely un-related to any of the pictures in this posts, Yes I have done that myself
Anyway here is an idea, and I don't know how hard this would be to implement, Sorry Admin
Keep having a monthly Photo-a-day, open posting
Have a challenge, monthly or like DpReview a max post limit
Have a specific size requirements limit
Thread will only show pictures: each picture have a drop down addition that can show picture information and comments made about picture
I don't know if this can be done with current Web design software, but I do think this would make the picture posting more interesting
Pete