Shane,
I trying to achieve the opposite. I want the Admin to add an image via field on the back-end (Add/Edit Product).
Then the Visitor can click on the button "NUTRITION" and the nutrition label will appear in a lightbox format.
In the images I had attached. You will see in image "02-add image to product" is where the Admin will add the Nutrition label image to the product.
In image "03-Button that is linked to image on front end" that button will be linked to the nutrition label image that the admin applied to the product.
Image "04-code for template" is what I had at the time of submitting this ticket.
I've since then been hacking at it and I've attached another showing what I've done. Still unsuccessful.
If you go to hidden link
You can scroll to - PRE-SLICED BLACK FOREST BONELESS SEASONED HAM (3rd item down).
Click on the nutrition button and see that it gives an error, but in the address bar you'll see that it is trying to link to the image.