And that's perfectly fine if we're dealing with an image that we've created from scratch. However, every CWBP map is a derivative work, and the ShareAlike element of the license on the original work--NeonKnight's FT map, for instance--states that any derivative works are bound by the same or a similar license. That is, the Non-Commercial element applies to all of the CWBP maps, no matter who made them.

From the Creative Commons FAQ, http://wiki.creativecommons.org/Freq...vative_work.3F

The one big caveat is for Creative Commons licenses that contain the ShareAlike license element (ie. Attribution-ShareAlike, Attribution-NonCommercial-ShareAlike). These licenses require derivative works (ie. the result of two combined works) to be licensed under the same license elements.
I may be misunderstanding things, but I want to be sure that we're all in the clear, just in case something funky happens. All we really need to do, as I understand it, is place a notice in whatever documentation we develop for the project that states something along the lines of "content creators are free to relicense their own work for other purposes, so long as all work submitted to the CWBP also retains the NC-BY-SA license. A creator's submission of work to the CWBP constitutes acceptance of this waiver of rights."

This way, the copyright owner (all of us collectively) can permit uses beyond what the license explicitly allows without someone having to come here and receive permission from every affected contributor individually.

We might have to give some thought to exactly how we word things so that someone can't come in, change the name of the continent, then start selling it as their own work, though.