Not every folder of contents is ideal for Cover Flow. A folder of folders or applications just gives you previews of their icons. Cover Flow in the Finder works best with folder of photos. As one Basics4Mac reader wrote to me:
I can scroll thru my art files very quickly and then drop the icons directly into Photoshop. Its MUCH faster than scrolling thru the Open command in Photoshop.Another bonus of Cover Flow is that it works with Quick Look. Hitting the Space Bar while in Cover Flow view will activate Quick Look, letting you see a larger preview of the photo without opening it.