I've actually thought about this myself. I'm getting married in September and I still have a box with love letters, pictures, etc. They aren't from just one particular boyfriend but several ex boyfriends that I had a significant relationship with. I don't have feelings for anyone of them anymore and love my fiance more than I have ever loved another person, but I don't want to get rid of that box. There are a lot of memories in that box.
I don't think I will be much help for you
My fiance knows the box exists and doesn't have a problem with me keeping it so I'm not getting rid of it at this point. Maybe one day I will be spring cleaning and realize it's crap taking up too much room and I will toss it, but until then I'm just gonna leave it at the back of the closet.
I think if you still have drama with this ex then it may be a good idea to get rid of it and get that out of your life. I don't think just having the box in itself means you have unresolved issues (I don't feel like I do) but if you keep going back to that box then ya, there may be something there.
Did that make any sense at all!?