I hate labeling people as "easily offended", but to complain about something like this seems excessive. If your father died would you presume to insist that your mother take down all his photos?
I guess if his mother entered his room without asking and hung up pictures of his dead father, most people would think that the mother was a bit inconsiderate. Of course, some people would claim that his room was not a personal space, and the house was owned and controlled by the mother anyway.
