What this produces is a deck of 16 cards, each with the proper front face. The back face, however, is the entire card sheet all over again. Doesn't the back-image-file make the default image for the back the image shown? The back image for the card set is never used at all.
As you can see, I point for the back to a specific location in the same (single) cards bitmap.
I assume that cards can have only one image file, unlike counters.
Yeah, I figured it out. I switched to using the card tag, but didn't alter the image to show the back on the same sheet. It's just one stupid mistake after another, sometimes.