If mbbored wants to keep the pictures, there's certainly nothing wrong with that. Five years is a significant portion of anyone's life.
But I also don't think that mbbored should feel in any way obligated, by anything, to keep them if she doesn't actually want them. Pictures often represent memories, and for good reason, but they're only mementos if mbbored sees them that way. If she doesn't actually want to keep them, they are clutter, even if she scans them and puts them on a CD or a thumb drive.
In addition, I don't think that getting rid of objects that are no longer meaningful is automatically equivalent to attempting to erase a past relationship. It is possible to decide there are objects representing a previous relationship that are no longer valuable or meaningful without wanting to forget the relationship ever happened.
Personally, I have pictures of myself with people I used to be friends with. Some of those former friends hurt me, in the method of their breaking off the friendship. I don't remember them fondly, and I don't particularly want to have pictures of us together. I've kept a few (for similar reasons as mbbored -- group shots or pictures of events/places that I don't have other pictures of), but I've gotten rid of a lot of others. All of them were, at one point, significant parts of my life. All of them were people I spent a lot of time with. And all of them hurt me enough that, while I've made peace with the end of the friendship, thinking about it doesn't make me happy.
From what I recall about mbbored's ex, he hurt her deeply. In her shoes, once I'd made my peace with the end of that relationship, I'm not sure I'd want to revisit it any more often than necessary, and I wouldn't want to keep objects that had no value to me outside of the fact that they were mementos of the relationship. The fact that my future children (or anyone else) might someday want to see those pictures would not sway me if I didn't have any reason beyond that to hang on to them.