Ah, I'm wrong, sorry.

I'd been inspecting the image elements to see why they were fuzzy on my retina screen, and didn't see those params - it's in the docs right there on the page though. In that case I'd just update the marketing site to fetch larger images so they look good on retina.

This is a fantastic project, by the way. The need for this comes up all the time for us (e.g. charts for emails).