OK so I have a cheat sheet, this is the only sheet I have that isn't Christmas themed and I can also make use of this on a card.
This technique can be used for any image that has possible layers. I think you will see what I mean with the example.
This first one shows the whole sheet and I am going to use the top right images. There are 4 in the set.

This one is the base image. If I were doing a set from the start I would use 3 or 4 of this image, depending on how many layers I could see.

Here are the other pieces

This is the finished set from the side. To show the depth between the layers.

and finally from the front.

Sorry for the pics, I was taking things a bit close but I think you get the idea.
As well as cards I have also made pictures using the same technique.