gnome-backgrounds : A set of backgrounds packaged with the GNOME desktop ( https://git.gnome.org/browse/gnome-backgrounds )
gnome-themes-standard : Standard Themes for GNOME Applications ( https://git.gnome.org/browse/gnome-themes-standard/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a gnome
For Paludis use this rsync : rsync://gentoo.zugaina.org/gnome-portage
If you have a problem : ycarus(-at-)zugaina.org