From Shiny Frog:
Image2icon can make icons from any file or folder, not just images
. You can apply the icon to any file, use it in templates or convert it in png or jpeg. Tired of your standard mac icons? Do you want to personalize your files or folders? Image2icon provides the fastest way to customize your icons, easily and free. It's easy as pie: drop an image to Image2icon, then drag your file or folder and drop it again to apply it.