I agree, each voter should have 5 votes to put where they wish (the nature of these polls only allows one vote per option per person). I don't think a vote ranking would be practical.
I think all ARC accounts should be allowed, but none younger than 30 days with fewer than 25 meaningful posts. "Meaningful" meaning more than just comments like "Nice tank!". I would volunteer to check these.
No usernames, however photo titles may be fun. I think we'll have to use our own discretion.
Photos should be downloaded and re-uploaded by whoever starts the thread. I would be willing to do this if we need a routine.
Order should definitely be randomized.
I don't think we need anything special for aspect ratios, the formatting shouldn't be too hard to figure out.