Tweak to Aitoc Custom Product Preview extension

Hi, We have succesfully installed the Custom Product Preview Magento extension into our shop. Module: [login to view URL] Shop: [login to view URL] Problem: When a customer image is uploaded then that image is in Front and the Catalog Image is in back. We are making custom smartphone covers and the image nog runs over camera in the image template. Solution: We have made a GIF image with a transparant center. We need the customer uploaded/selected image to show behind our template image. As we make more products, this feature must be switchable in the Magento admin per product (selectable Front layer/Back layer image). Best regards, Marijn