Icons from icon10.png and icon16.png are taken from Fugue and Diagona icon sets by Yusuke Kamiyamane:
http://p.yusukekamiyamane.com/

Yusuke Kamiyamane's icons sets are astonishing, offering over 3K icons.
If built-in icons are not enough for your app, we advise you to consider icons from Fugue and Diagona icon sets.

Fugue and Diagona icon sets are available under a Creative Commons Attribution 3.0 License.