It seemed like the pictures were all of the same girl and family or group. The way some of the text was spelled out implies, to me at least, that it was a personal threat. "You were warned" and "this isn't over."
The images were scans of film photography that appeared, to me, to be from around the late 80s to mid 90s. Estimating the victim to be around eight years old gives us a current age of around 30-40.
There was another where a girl seemed to be a friend or family relative, rather than a sibling. The way they are acting in those pictures implies this was just another day to them - or "fun time with uncle rob" - so whoever these girls are probably came to realize what was being done to them later on in life.
My bet is that this person is currently in a position of influence or key decision making, somewhere, and is known to be watching this board. The way it was dropped suggests this person probably has agents watching this board or using an auto-archive script. Mainly my gut. You would use a different platform if you weren't sure you'd hit your mark.
Thus - someone is thinking they are going to intimidate someone with those pictures. Not public harassment - circulation among select people in this person's social or business groups.
Could also be someone's child and the camera/film could just be old to give the appearance of it being much earlier.
That's my assessment of it. Going deeper would require me to actually download the images and do things that are reserved to law enforcement.