Although we've been happily married for 40 years, it mustn't be forgotten that I am DH's second wife. First marriage was childless and lasted a very short time.
He had never told our 3 DCs about his marriage, but I have. I have even shown them photos of the first marriage [kept in a drawer]. DH doesn't know but I feel it is very important for them to know something about their father's past. If it came out now, it would be a horrible shock for them.
So, yes, keep the photos of exes, particularly if they have died; label them - but if you don't feel that it is right to keep them on display, that's fine too.