Comment 7 for bug 274714

Dean, unfortunately "royalty-free" is not good enough. The image needs to have a license that explictly allows certain things. For example, the license must allow modification, and re-distribution of modified versions. Without a license, such things are not allowed.

http://www.ubuntu.com/community/ubuntustory/philosophy has some information on that.

Thus, unless such a license is found, I have to reject the icon.