Ostfriesland is an open source GNOME-Shell theme specially designed for the GNOME 3.6.x desktop environment. It is based on the Frieze theme created by Jacob van Mourik.

For detailed installation instructions please see the following tutorial created by Softpedia: http://news.softpedia.com/news/How-to-Install-GNOME-Themes-in-Ubuntu-11-10-231213.shtml