on our 9/6 cruise (7 day) we asked if they would hold photos, the asnwer was no. They did say, however, that no photos get thrown away, so at the end of the cruise you could ask them for a specific set of pictures that you can look through (try to remember the day and the place/character in the photo)
also, we bought the 10 photo plan, and we were allowed to exchange up to 3 photos if we saw something we liked better later in the cruise (which we did with no problem)