gdk-pixbuf is currently unconditionally dependant on gnome-libs which makes it impossible to install certain gtk1 apps without pulling in gnome 1. I don't think anybody even uses gnome 1 anymore.... Anyway.. it can be fixed by wrapping a gnome? ( ) around the dependancy which then at least allows you to use -gnome in package.use.
search It is even noted in the ebuild why this was done : # We need gnome-libs here, else gnome support do not get compiled into # gdk-pixbuf (the GnomeCanvasPixbuf library ) *** This bug has been marked as a duplicate of 7693 ***