Needing Advice: My fiance' still has nude photos of an "ex"?

Throw a log in your fireplace, ask him to bring the box in, and then have a little living room bonfire. Have a serious talk with him letting him you need complete transparency or you're not going to trust him enough to go through with the marriage. And then stick to it. Trust me, you do not want to live a lifetime with a man you cannot trust.