I agree with Kittie and Rin's idea and input. Have the judges give their votes but don't exclude the public fully. It's good to keep everyone involved when voting. If you could figure out a way to bring the community in with serious and unbiased votes than that would be amazing.
Prizes. Hmm, I like the user bar idea. Those shouldn't take tons of work to create and you can reuse the base for them and just add a name, date, and position? I don't know. I also like Jay's idea for the coupons. 100 for First, 50 for second, and 25 for third. It seems to go down the list evenly and fairly.
Sorry, I know I'm not that great of a graphics person but I thought I'd just agree with what I liked. :D
OH! I also would love to see a specific forum for signature competitions. The originality section is rather messy and the competitions take up most of the space, so I believe it deserves its own section.