Description of problem: After a fresh f20 installation with mate desktop, lightdm displayed any icons. This can be simply fixed with editing /etc/lightdm/lightdm-gtk-greeter.conf Using here icon-theme-name=gnome or icon-theme-name=mate give the symbolic icons back. It seems that lightdm use wrong default values for a icon-theme or can't read the defaults from fedora, which is gnome-icon-theme. Overwrite /etc/lightdm/lightdm-gtk-greeter.conf during rpm build process should be the simplest solution to fix this issue. Version-Release number of selected component (if applicable): latest for f20
See gnome-themes-standard bug #999158 for details, and workaround (until it is fixed properly) *** This bug has been marked as a duplicate of bug 999158 ***