This works absolutely great.
Just do the following 3 things to end up with a great result:
- Create a transparent PNG with your icon
- Set the right background
- Choose a nice and short title and press "Save changes".
Your done! If you now pin your site to Windows 8, you'll see the great new icon. Wow, this was easy. Thanks so much.
Want an example? http://www.dartblaster.de