https://forum.kde.org/viewtopic.php?f=288&t=133585#p359065 mentions saving arbitrary data into image headers.
As far as I can tell, this cannot be done with python scripting at the moment. If it can, I propose we at the very least have an example python script for it ready.
If not, we need to think about how we make this accesible? The description data doesn't always automagically store itself into the image file...