You may want to try listing this in the jobs board if you do not get any further replies here. This could be done with the use of UE4/Digital File Pro and eCart to edit the product details page to add in the upload functionality and editing the cart to have places for the new images. If you are not familiar with using these tools though you might find this challenging to accomplish. You should start out by checking the included help and support pages for these products to get an idea for how to use them in certain situations.