So I'm still annoyed about the whole thing with Getty Images. So I happened to do a quick search on "Getty Images Licensing Compliance" and came up with a number of posts addressing "the Getty Images Extortion Letter".
This article, How to Respond to the Getty Images Extortion Letter, is great. It's from the Art Law Journal. It provides a comprehensive explanation of what's going on as well as a template letter for your response.
Here's another post from a hacker/security site with a more extensive cataloging of Getty Images extortion racket.
I'm not going use Getty Images any longer and I recommend you avoid using them as well.