There's also another tool who lets you change the Library icons, and it's simpler
From askvg:
Librarian is an excellent piece of software created by our friend "Happy Bulldozer aka hb860". It allows you easily tweak Libraries in Windows 7.
It is a multi-language application which allows you to:
* Create a new library with any folder(s) inside
* Change library's icon through standard Windows dialog
* Rename library
* Change content type of new or current library
* Change "default save location" option
* Change "Show in Navigation Pane" option
* Show library as XML
Download here:
Librarian: A Library Manager for Windows 7 - Tweaking with Vishal