It could be a photo of your pet, someone you care about, some place you love... By this way, your photo will be algorithmically set in stone and spread all over the world, everywhere PlantUML is installed, even if no one but you knows about it...
There are two kinds of Dedication:
Public: the special sentence is publicy written in the code of PlantUML, so someone searching into the code will be able to find it and then see your photo.
Private: only SHA-512 signature of the special sentence is in the source code (as the encrypted photo). No one can guess your special sentence, neither see your photo, since it's encrypted using the sentence itself.
We have made a demo with the special sentence Write your own dedication!
It works in each deployed instance of PlantUML over the world.