If you really think about it,posting wips for a challenge seems to make the artwork a combination of everyone elses thoughts and ideas. This is fine for regular gallery images,but as a challenge,should'nt the be kept a secret until finished?As far as the prize goes, great idea to bring everyone together as part of a community.
Just remember to: Look at the full size entries.Be honest in judgements.Favor no-one,(just because someone may be a close buddy,have confidence that they are a friend and understand it is only images we are talking here.) Pay attention to what the output is,and what the rules of the challenge are. Most important..Have Fun

"The happiness of a man in this life does not consist in the absence but in the mastery of his passions."