1. Use the ebuild mentioned above to copy all the icons to your /usr/share/icons directory. I will assume the icon folder that you use is "gentoo."
2. Grab the following file-
http://home.post227.org/~cah2240/index.theme
Place it in /usr/share/icons/gentoo.
3. Next make in /usr/shareicons/gentoo the following directories. apps, dev, emb, fs, mime.
4. Place in the directories the icons that you want to use, they must be renamed to be the same as the actual program name. Ex. the mozilla icon must be named "mozilla-icon.png" and placed in the apps folder. A guide to naming can be found at
http://www.ajgenius.us/gnome/gnome2-icon-themes.html
5. Go into the 'Theme' settings menu and add to your choice of theme the Gentoo iconset.
EDIT: I've abandoned the tar idea because of the duplication I found in the icon set. If one was made it would probably only satisfy a fraction of the contributors.
P.S. Tell me if I am completely wrong in regards to it.
If Windows is an OS made by professionals, and Linux is one by amateurs. Ponder this, Noah an amateur built the ark, professionals built the Titanic.