I did this awhileeee ago and it was a lot of fun. Essentially, it'll just be like bracket style starting with 32 or 64 people (depending on interest by the blog expiration).
So first 32 or 64 people to post will be paired up randomly and thrown into a 2 person poll. Winner of the poll will move on to the next round. This continues until 2 people remain and winner of that poll will get a gift of their choosing!