I didn't like the Windows 7 user icon files, and prefer the Windows Vista ones, so thought I'd write a guide to how I changed them. You can't change the Contacts and Desktop user folder, but as I don't use these, I just set them to hidden instead.

Obtain a Windows Vista imageres.dll file by copying it from a Vista machine (Found in Windows>System32/SysWOW64). Place it in My Documents and rename it to something like imageres2.dll. (The file is too big to upload as an attachment).
- To change the desktop user icon, right click on desktop>Personalize>Change Desktop Icons and click your user icon and click the "Change Icon" button.
- At the top, it will have a field where you can browse for a source file. Browse to and select the imageres2.dll file. It will open all the Vista icons allowing you to select the Vista user folder.

- To customise the other folders, go to C:>User>Username (You can't edit user folder icons by just clicking your folder on desktop).
- Right click on all the folders and go to the customise tab and click "Change Icon". Search for the corresponding icon.
- Repeat this for all steps. Remember the Contacts and Desktop icon can't be changed, so I just set these to hidden as I don't use them.
- Once all the folders are changed, you can set the imageres2.dll file to hidden as well.
Edit: When you're on the Desktop Icon settings, uncheck the box that says "Allow themes to change desktop icons" so when you change your wallpaper or taskbar colour, the icons don't revert to default.