Icons Created by:
-Chromakode
gmpc-no-cover

Cube:
gmpc
gmpc-tray-*

-Gnome Default Theme (author not in theme file dir?)

-Tango project (public domain now a days)
(http://creativecommons.org/licenses/by-sa/2.5/)
media-artist
media-stream
media-repeat
media-random
stock_volume (renamed to gmpc-volume)
audio-volume-muted
audio-volume-high
audio-volume-medium
audio-volume-low

TheSheep
- media-playlist
- tag-browser
- playlist-browser
- playlist-search-browser

Other unknown

Chymera:
License: Free Art License (http://artlibre.org/licence/lal/en/)
- stylized-cover
- stylized-no-cover
- stylized-fetching-cover
- artist-fetching
- no artist

Zeltak:
Humanity icons and the tray icons.
