Thanks for all of the replies. To answer a few of the questions many of you have asked: the photos are not on display, they are digital images that I found when I was using his computer. I feel embarrassed to say, but I found them in the trash bin of iPhoto, but I think they are actually saved somewhere else on the computer b/c when I right clicked on some of them, it showed me the file path and the folder they were in with other photos.
So, I feel a bit conflicted about whether I should bring it up again. I say again, because he and I have spoken about my feelings around pictures of his exs (at the time, I did not know if he had any naked looking photos, but I said that if he did, I did not feel comfortable with him keeping them, and then added, at least not in a place where I would run across them - in retrospect, I realize that is not true, and I feel uncomfortable with them full stop!). Anyhow, he was very respectful and sensitive to my feelings and we did not speak about it more afterward. I am respectful of his past and also understand that photos may not mean the same to him as to me because he works in photography - so some of these images may not be "photos of his ex" but rather "examples of his work" (I am just guessing and trying to give him the benefit of the doubt).
About the naked photos, I did not find tons only two, and they were indeed quite artistic (meaning you couldn't really see anything) and not sexual. They were also of a very old ex who I have met and he considers a friend (granted he hardly sees her since we became serious ~ 3 years ago). That said, it is still uncomfortable for me to have seen these photos - and I feel bad because I found them and now feel uncertain if they were truly deleted or really saved somewhere else on the computer (perhaps some of you are familiar with iphoto, and can answer this question). In any case, the other side of me tells myself that I am being silly because I trust him fully and we are able to speak about things openly and he is very respectful of my feelings (plus, these women are not part of his life, so they are really just images, nothing more). Anyhow, I have been mulling this over for the past few days, and part of me wants to return to the computer and simply delete them! But I know that would not be respectful at all; and it might be downright silly if they are actually deleted and the file path that iPhoto shows you from the trash can may not mean a damn thing
Anyhow, ladies, thanks for letting me get that out.