If they won't be deleted they need to be assigned to another user or at least hidden from public view. Currently they are abandoned which makes it very hard to deal with them.
@
sonnb, please tell if you consider this a bug (and take care of it) or not. If not, we need to code this deletion extension ourself, because each additional deleted user makes the situation more complicated currently.
In my opinion pictures of deleted users cannot be left abandoned and continued to be served to the public without any chance to administrativly handle them later.