You can find plenty of icons for GNU applications at gentoo's homepage:
http://www.gentoo.org/dyn/icons.xml
I simply think that the rounded icon that gentoo uses are the best icons I ever came across. Worthy even changing all your icons for gentoo's.
Regards!
P.S: a little skill with gimp should be enough to make yourself an icon. Copy and paste an image from blender.org and edit it
. Not only it gives your desktop personality but, well, gimp is fun and most likely you will need to use it to texture your blender creations
