These are simple cards with a standard surface material. A single image is driving the base color and opacity (alpha channel from the image is driving the opacity).
I've included viewport screens here of the cards both with and without the texture, and then an IPR render that shows my problem--there are spots in the render of opaque black. This should be a simple fix but I'm not sure what to do. Increasing the transmission rays and transmission samples didn't have an effect.