We had 17 people on an RCI ship three years ago and requested a picture of the group, the ship was very accommodating on one of the nights that they had a formal, we got together and the photographer snapped some for us. Be on time, they have tons of groups having this done. They also required us to purchase one if advance and then it was our choice to on how many more to purchase.
I found that on longer cruises the photos are not always displayed for the whole cruise, maybe just a day or two. Enjoy your cruise!