There are so many members that it's really hard to choose a few, but the focus should be on picking out one indiviual for a certain personality. We shouldn't be nominating somebody cause we like them. Pick however many people you want on the poll--as Neel said, around 15. Then pick fifteen fairly unique personality profiles, and choose the member that best fits each one. A lot of people are great members, but aren't really unique enough to warrant getting on the poll.
...I was going to try to make an example list, but this is harder than I thought.
