I had a similar situatin with my husband when I first moved in only i found pics. I talked to him about it though, he said that they were not an issue for him and he took all of them and threw them away. But that was his decision. I think you should try doing the same. Talk to your FI, tell him how you feel and how you felt finding them, and ask them what he wants to do with them. I agree with Alyssa that as much as you want to throw them away, you should probably let him make that decision b/c its not really your place to throw them out.