The plugin is almost exactly what we've been looking for, just a couple of suggestions:
Can the % markup be removed? We really don't want to give our buyers an exact display of how much the price change is. For instance, we're a news website. If someone wants to buy an image for personal use its license is only $9. If it is being used for commercial news broadcast, the license is $135.
We really don't want the buyers to be able to see that the commercial license is nearly a 1500% markup - it doesn't really serve any purpose other than to deter them from purchasing.
An overlay on the image in the story would be great. We currently use the standard wordpress image insert for our stories. It would be a very useful feature if, when people's cursor moved over the image, a small "license" or "buy" button popped up in the bottom corner somewhere. There are a few Pinterest plugins that currently do this.