Even though the relationship is over doesn't mean the memory is. Keeping them does not have to mean that we want to get back together with them either.
Are they erotic pictures or just regular pictures? If they are erotic photos, then I see it as nothing more than porn on a closer level (they have the phone number to reach out and touch that person). If they are regular pictures, I don't think it's a big deal because it is a memory and you should be able to show those to whomever. I have regular pictures of my ex's and I would only hope my husband would not be upset to see who I use to date before meeting him.
I've kept mine usually because I looked good in the pic =p ha ha
I have a couple pictures in boxes with old letters, prom memorabilia and the like. For me, it's just memories. It doesn't mean I want to get back with them or think about them "that way". I had a good time with all of them, but they're ex's for a reason :)
In some cases it is because they still like the person, another thing is that if they went out that person obviously found the one they have pictures of attractive at one point, it also can bring back good memories.
Did you ever know someone that was backstabbing and fake? Yet when you try to warn people about you, they see the fake performance as real and get mad at you for it? If so, then you will totally see...
When giving tough love to a friend or even someone you don't know - I would like to bring up a few points that may seem "considerate" to think about, before advising. Tough Love isn't for everybody....