Seven theme provides icons meant to integrate the application's look and feel in a Windows Vista / 7 environment, in order to provide more familiar visual metaphors to users of those systems.
Icons are derived from:

Tango Desktop Project

Original reference: http://tango.freedesktop.org/Tango_Desktop_Project
Original license: Attribution-Share Alike 2.5 Generic http://creativecommons.org/licenses/by-sa/2.5/

Crystal and CristalClear

Original reference: http://www.everaldo.com/crystal/
Original license: LGPL

NuoveXT

Original reference: http://nuovext.pwsp.net/
Original license: LGPL