Looking for opinions. Do you think this is weird?

It's possible that your mother's just trying to keep the peace and not stir up some kind of crazy hornet's nest, however, as a mother myself, there is no way on God's green earth that I would give the time of day to my daughter's abusive ex-husband. Sometimes it's not enough to say "This is weird". Perhaps you ought to sit her down and tell her gently how her behaviour is making you feel. My concern is that her acceptance of, and attachment, to your abusive ex-husband may serve to validate his reprehensible behaviour. Sure, they may only be photographs, but they represent a connection to a dark time of your life; a connection that ought to be severed (just like certain parts of his body lol).