I am collecting a few HDR titles and have been labeling them "<movietitle> (HDR) (<year>)". That way they can be distinguished from Non-HDR versions of the same movie. For Example:

Wall-E (HDR) (2008).mkv
Wall-E (HDR) (2008).jpg


Wall-E (2008).mkv
Wall-E (2008).jpg

Each in their own, respectively named folder.

Mezzmo refuses to automatically use this poster for the HDR titles. It works great for the non-HDR, though. It's universal and repeatable every time.