http://www.themes.org/ is the only one I know about that has Gnome themes. I think Gnome's popularity has really dropped since KDE 2.0 was released.
I use KDE most of the time now and I only used Gnome before. I do like the Gnome 1.4, although I think Nautilus is WAY to bloated. It does run pretty good if you turn off all the garbage. We will have to wait and see what Gnome 2.0 has in store.