Quartz92,
I am all for you being in charge of the competition, that's totally fine with me. I like your idea for the naming scheme of the photos. I think they should be posted in the gallery as you suggested, but with direct links to them posted in a thread that will be used for the competition.
I'm not sure about whether it should be the members only nights or 2 weeks. My concern would be that there might be an overwhelming amount of photos if it's open for 2 weeks. We'll see what others think about this and decide as the time gets closer, I think.
I think it should be animals only as well. However, maybe there could be one winner for best polar bear photo, one winner for best arctic wolf photo, etc.