Lush icons pack theme first released for Gnome and now ported and mantained.
Lush are brand new SVG icon theme from David Vignoni, first released for KDE and now ported and mantained for Gnome by Christian Fredrik Kalager Schaller.
Go to Desktop - Preferences - Theme
Click on Install Theme button and chose the icon archive.
Then go to Theme Details and go to Icons Tab and chose from the list the icon theme.