Accepted licenses for non-code contributions

[Albert Astals Cid]

We have
http://developer.kde.org/policies/licensepolicy.html
http://developernew.kde.org/Policies/Licensing_Policy
for code contributions but i was wondering what are the "accepted/suggested" 
licenses for non-code, specially graphics, as there is people willing to send 
me maps for KGeography but they say the images they used for basing the map 
on are
 * GFDL with no Invariant Sections, no Front-Cover Texts, and no Back-Cover 
Texts (wonder why one would want to license an image with GFDL)
 * Creative Commons variants
and don't know if it is OK or not.

Are that licenses free enough for us? Specially i think there are some 
Creative Commons licenses that are non free but others are, so if someone has 
some knowledge to share there i'd be very happy :-)

Thanks,
   Albert