ICNS - Macintosh Icon File ICN - Macintosh Fork File ICO - for Windows XP/Vista usage iContainer - for use with Candybar
There is also a customizable version provided (in PSD format), so you can change/add the wallpaper or desktop screenshot of your choice to the scree. I also created, for ease of use, the exact area where the desktop screenshot should go as a layer mask, so to activate it do these steps:
Place your desktop screenshot or a wallpaper, and if it doesn't fit properly, go to menubar (OS X), or File (Windows) > Select > Load Selection. From the drop down menu, select "Screen Cut", and hit ok, and this will make an automatic selection around the area where the desktop goes. Then just hit delete on the keyboard, and it will delete the excess area on the desktop. Enjoy!