Here is what I did to make one...
Find an IP with a live folder and extract the 3 images, make your own folder parts in photoshop (or whatever editor you use) using the extracted folder images as a background being careful to position yours over the left folder edge of the ones you extracted. Then delete the background and save wherever you like.
Once that part is done, open Icondeveloper and create the icon. Then it's just a matter of putting it in the IP you want it in.
I know that is a pretty simplified way of putting it, but if you need a bit more detail, just let me know. 
