Allow discounts that are specific to digital images
Yes! My portrait packages include 20 digital files, but I often upload more for them to choose their desired images. In ShootProof I created a discount for the 20 images and gave that code to my client. If they wanted to purchase more they simply paid the difference all in one transaction.
Now, the only way I can see a workaround is having clients do 20 favorites then me sending them those files. Then they have to cross reference those files to ensure they aren't purchasing them by accident.