I think I would prefer impartial judges above anything else. Showing the judges the sprites without telling them who made which sprite would be ideal, though I think to properly critique the sprites they would have to know a bit about spriting; if you just showed them to random PC users, you would need a pretty big sample size to eliminate people that voted just because they like Wooper, or like the color yellow, or something.
Maybe a rotating panel of judges? I know that Scarf is active on PC, but hasn't been posting in the WPC threads.
edit: While I understand why a rule against double-posting exists, sometimes it doesn't really work. For example, I'm editing this post a week later to talk about the latest WPC so that I can avoid double-posting, but nobody will know there's a new post here unless they actually come to the latest page of this thread, and only if they read this post. Ah well.
I'm not exactly proud of my entry into the competition. When it launched I made a list of fourteen Pokemon I thought might work well (including Castform, Spoink, and Mawile), and originally intended to make an evolution of Sharpedo with a large protruding forehead. I ended up being unable to find the time for it until tonight, and after trying several things out, I just couldn't come up with something that I liked.
With only an hour left to enter, I shifted gears and started thinking about what I could do with a Chimecho evolution; since Chimecho is so simple, it wouldn't take much to make it more complex. After a bit of research, I decided to base it on a Japanese pellet drum, more for lack of a better idea than anything else. I actually kind of like the concept, and think it could be adapted into a cute sprite, but rushing as I was and with less than an hour to go it didn't turn out as well as it could have.
It's not a terrible sprite, but it's sloppy in places. The linework is clearly very basic (how quickly circles and curved lines can be made is part of why I went with this design), I completely forgot about the diagonal striped pattern I was going to put on the handle, and the face... Well, I was down to the last ten minutes. I'm likely not going to win any awards for this one, but the point is to have fun, right? With that in mind, some kind of speed challenge may be interesting in the future, though I'm not sure how that would be arranged.