The module allows you to customize product images by adding an alternative image and a mask image
Normally, you would display a cover image for your product and optionally some combination images, but generally, these images are only suitable for presentation purposes.
You have a solution where you can replace the presentation images with images that are more suitable for design.
Simply click on the empty rectangles and add an alternative image
The mask image can be used to cover the design that is outside the product
To create a mask image, simply make the design area transparent like this
That way, the excess design will be covered by the mask opaque area like so
So anything that goes outside the design area will be covered by the white area of the mask
You can include some semi transparent shadows in the mask to give a more realistic look to the final result but that would require some graphics editing knowledge