I think that Wikipedia's mascot should be an image which anyone can draw on and add to at any time. Perhaps some sort of Java applet would be useful, with a variety of drawing tools and a built-in edit history of the image so we can easily revert it when people add the Goatse image or other copyrighted clip art. We could do the same thing with the Wikipedia logo in the upper corner of the web pages.
No, I'm not actually serious. :)
Perhaps we could use Frankenstein's Monster as our mascot, to represent our approach to article writing?
Still not serious. :)