The Art Team maintains the following base icon themes:
gnome-icon-theme - base icon theme for the desktop, aiming to cover the icon naming spec defined iconset consisting of generic icons. The icons follow the Tango style guidelines.
gnome-icon-theme-symbolic - and extension module to gnome-icon-theme for specific context (OSD, panel, entry widgets). Icons will eventually folow the widget theme in terms of colors.
gnome-icon-theme-extras - specific filetype and device icons extending the base theme. Optional.