EDITED:
GPL needs "source" to be available, which - in case of music or 3D work is not always easy to obtain. Some of contributors are not easy to catch, others won't give eg. their samples. All my assets here and elsewhere are under WTFPL, so anyone can relicense it as he/her wish, but thats me (and semolina too?).
Barra knows the licensing subject best.
My point of view is rather simple - do not change licensing of assets we already have, keep new things coming dual-licensed as they are now (or whatever - but just when we stick to a license - it should remain consistent) and keep an eye if source files are given with artwork, cause we can eg. improve some things in 3D artwork later on.
2D graphics is simple in this case: PNG files we use are lossless. With time (getting contact with authors and asking for relicensing stuff or changing some artwork) we may achieve consistent licensing.
Once again, shorter. For me - GPL or CC is just a matter of letters, I want my work to be as available, as possible. PARPG always gets lossless 2D graphics.
But sound artists and 3D designers may have other approach. For me .ogg is enough, but is lossless .flac GPL-compatible?
And, mostly with 3D work we may want to re-render (you know this one:
http://parpg-trac.cvsdude.com/parpg/ticket/251 is a good case for "must re-render" state) some things, so we need all "source files" for 3D anyway.
Will we be in main branches of major Linux repos with CC licenses?
