is there a halachic basis for not displaying pictures of women?
The Rambam states women should not leave their home too often. The Rambam says once or twice a month at most. Shulchan Aruch paskens l’halacha that women should not leave the home often, though doesn’t specify a number. The reason for this halacha is so that men shouldn’t see them too often. And this halacha is applicable when women are going from their home directly to another location (i.e. to her father’s home, in Rambam’s example), without lingering in public. And, obviously, the women are dressed completely tzniusdik even those few times they do go outside.
A photo of a woman publicly published can linger in front of men indefinitely. And privately. So it is even worse than a tzniusdik woman going nonstop from her home to her father’s home while dressed entirely tznius during the very infrequent short trip in public.