Dennis was kind enough to talk about how he approached the content on his image pages to get optimal results in searches (in the thread referenced in the OP). I experimented with getting a handful of my own images to get a "green" dot from the Yoast SEO plugin and wrote a blog post about the process for anyone else who is interested to take a look at

http://www.digitalbristles.com/symbiostock-image-pages-go-green/