Hi Jamie. Being the most graphically-inclined member of the ComDev team, I would love to design new logos for those wikis, but I have no experience (or skill) at creating vector graphics (SVG). For a professional job like that, you'd be better off hiring a graphic designer/artist either on your own or at crowdsourcing sites, such as logomyway.com and designcrowd.com.
In the spirit of collaboration, I think I might follow your suggestion to go the DesignCrowd route, and turn this into a community-run contest. Once I set up a project and define my desired outcomes, I'll promote it on the sites and then let the community vote to pick the winner.
I don't suppose Wikia would be willing to help me with the project costs, would they? (I know Jennifer Betka is just sitting on a pile of cash in her office that she doesn't know how to spend. Right? Seriously though, is that a thing that could happen?)