With Clipalizer you can easily create your own custom webclip icons for your favorite sites. All you need to do is visit Clipalizer put in your favorite sites name and URL and upload a 5757 PNG icon. Clipalizer will then give you a shortened URL to plug into your iPhone which will then allow you to select your custom webclip. That custom link that you made will stay alive forever so you can always enjoy your custom icon.
This custom link is simply a redirect that also houses your customicon so the iPhone/iPod touch will use your custom icon. They promise that the service is free and private, with no personally identifiable information being collected.