Using thumbnail of the title slide

I want to show a list of my presentations with the title and a thumbnail of each. I know I could do a screenshot of each one and use those, or use Iframes, but is there an easier way?

I hoped I could use the Cover image, but how? Or maybe the plugin could store an image of the first slide and I could use that?

telizarose in her How to Create a Slide Deck presentation (excellent – thanks) under 6. Set up Social Sharing Images hints at the possibility:
“If you’re going to share this link anywhere online, set up your social sharing images so that they display something descriptive of the overall presentation. Otherwise, if you didn’t set a cover image, your display image ends up becoming an image from inside your slide deck.”