Put your own content in shopping cart with only 5 step in e.q. Photoshop or Gimp. Content of image are 3 member. Back cover, front cover and black contour of front cover. This is the procedure:
1. Image/Extract black contour of front cover in separate layer
2. Select/Color Range/Shadows of selection (this make selection of front cover contour)
3. Select/Save selection of black contour
4. Put front cover over black contour in separate layer and get Select/Load selection
5. Select/Inverse and delete all white fields around front cover
So you have now 2 layers (Front and back cover) and between them you can put your own isolated content (View sample on image).