I've worked on several products where we built a community forum section. We chose to build from scratch because the existing threaded forums (vBulletin[1], vanilla[2], phpbb[3]) all used the same general layouts (threaded discussion, pagination, tables for layout).
Having worked for Internet Brands (who owns vBulletin and several hundred sites that use it), I can say that appearance is not at the top of the list for forum owners. The things they look for are security, spam prevention, performance, management tools, and plugins. Themes aren't a priority because people go there for the content, not the looks. You might have an angle if you made a better interface for one of the existing forum platforms.
Thank you for the input. I can see why the backend and operational pieces would be far more important to the people to actually HAVE to manage the site. Maybe this is just a plugin idea...
