The magic is likely courtesy of the fact that my post has a meta tag for og:image that includes (or transcludes) that image from Naughton's website. It's something I added in for syndicating to sites like Twitter or Facebook to add a little visual interest. I suspect that whatever you're using to unfurl the page on your site is picking up that data to display it as context for your like. You'll notice that the same photo appears on Twitter as well: https:/
I'm currently doing this with fields in the All In One SEO plugin for WordPress, though I suspect that Yoast and other Open Graph meta related plugins will do it as well. More often than not I use the functionality to force particular photos to be shown in syndicated services. Usually I'll also transclude the photo in my own post, so in most cases you probably wouldn't have guessed. Sharp eye for having noticed here Jeremy.