GraphicsMagick is a replacement for ImageMagick. Now www-apps/gallery depends only on media-gfx/imagemagick.
Sorry about the mass reassignment, but this undertaking really shouldn't burden bug-wranglers further.
Wojciech, did you succesfully run gallery with media-gfx/graphicsmagick[imagemagick] ?
# Image Processing Library - In order to automatically generate thumbnails and resized versions of your photos, Gallery requires either ImageMagick or NetPBM. Gallery 2 additionally supports GD and GraphicsMagick
Yes, gallery3 with GM on Gentoo run perfectly fine (http://woju.homelinux.org/gallery3/20100914-Tatry), but haven't tried gallery2.
Fixed in gallery-2.3.1 in CVS.