AIO Over An Envelope of Pictures of His Ex That My Boyfriend Keeps Near His Bed?

I (21F) and my boyfriend (20M) have been together for a little over year and I would say things have been going well. We have a lot of shared interests like video games and movies and have made a lot of great memories together. But recently, after helping him clean his room, it feels like he may not be completely over his ex.

I was helping him clean and organize his things after his room had gotten a bit messy (he works late nights and is often too tired to clean and tidy when he gets home). I stumbled upon a blank envelope on the shelf above his bed and asked him what was in it. He seemed really excited to show me what was inside and when he pulled out a stack of 20+ photographs, I wished I hadn't asked.

He flipped through every single photo and showed me old memories, pictures from their first date, prom night, other random dates and happily retold the story behind each one. As if he was reminiscing on good times. For context, their relationship ended really badly from what he's told me. She cheated on him multiple times made fun of him for being skinny, and made him pay for her hair, nails, food, etc all while he was working part time at a fast food restaurant.

I asked him why he kept the envelope near his bed and in his exact words, "I don't want to lose it since I want to show these pictures to my grandchildren someday."

This made me feel really insecure about our relationship and I feel stupid about it. Why would you want to show pictures of your toxic ex-girlfriend to your grandchildren? And why was he so excited to show them to me? I asked him if he would throw them away or not keep them next to his bed since it made me feel a little uncomfortable and he was adamant on keeping them in the spot he has them in. 

I know it's not my place to tell him what to do, but it feels pretty shitty to know that he has printed photographs of another woman, 5 inches from where he goes to bed every night. He doesn't even have an images of us printed anywhere. Am I an overacting for wanting him to throw them away or move them? Is it really nothing?

(The bed is one of those with the little shelves in the headboard. He keeps books and other stuff in there but why an envelope with pictures of your ex?)