Think you missed the point completely. You can also use Fireshot as a firefox add on, or a multitude of of other web based applications and functiosn to create screenshots and screen shares.
So, use your method and get a screenshot of as pecific url into your
WP site. Time to do 40 = ??
Using my approach, i use shortcode in my
WP theme(any), and add the line with the url and the size dimensions, and done.
I don't won the site creating the API at all, the only thing is havent found many of these screen shot services that can grab inside pages with an API.
So using shortcodes, simple and easy to dynamically add multiple urls and repeat the process as you wish. I have found 100 free uses a month plenty to integrate into a
WP site.