We have found a Windows app called, LiBraryIconsChanger, which is a simple application that allows you to change your Windows 7 library icons to give them a new look. With the help of this application you can easily replace the .ico files of the Windows 7 library icons with any icon you desire.
All you need to do is just launch LiBraryIconsChanger, select a library icon (e.g. Documents), and click on ‘Browse Icons’ to select a replacement icon and then click ‘Restart Explorer’. Doing this will replace the library icon with your selected .ico file.
You can do this for each Library icon one by one to get the custom icon look. All icons can be restored by clicking on the ‘Restore Default Icon’ button within the app. This guarantees that you will be able to revert back to the changes and will not be left high and dry to find and replace the default Windows library icon files.
Like changing icon within Windows 7? Check out W7 Superbar Icon Changer.