OK... so here's what the Royal benefits states on their website...
Diamond, Diamond Plus, and Pinnacle club members receive a free any size photo of your choice from your existing photograph selection. Special requests such as reprints, copies or modifications cannot be accommodated.
So here's a potential way of how to handle it... whenever you wish to select a picture of someone else as one of your perks, give the photographer your sea pass as they take snap the picture. Be the dining table, formal night staged area, getting off the ship while at port, just hand themyour seapass and the image will modt likely be placed under that account. It should then fall into your selection.