I think anyone should be forced to delete suggestive photos of someone if requested - especially an ex, who may be posting such photos as revenge. Posting suggestive photos without someone's permission is a form of online bullying and all bullying should be illegal. The internet needs rules and laws just like the real world.
Although it is probably better not to allow anyone to take suggestive photos of you, people should have the right to control the use of their image. It would be terrible if an ex put out these kind of pictures, and morally should delete them. If they don't, legal means may be the only way to go.
This goes back to the concept of be careful of who you allow to have 'naughty' photos of you. Legally the person who took the photo is the owner and had full control of how and where it is viewed. If they post your suggestive photos in a non-commercial venue, such as Facebook, there nothing you can do to force them to remove them.
Once something digital is released into cyber space, no one has any control over it. If you don't want your ex to have suggested photos, you should take precautions in all relationships and not take said photos or else program them to self-delete after being viewed. It is a risk you assume by exposing yourself. In all other situations, the person who takes the photo owns the photo, and that should not be any different just because the person in the photo regrets having allowed it to be taken. Even if your ex were to delete their copies of the photos, that does not guarantee they do not exist.