I don't remember what photo you're talking about xD Could you post a screenshot of it or something?
But honestly, there are so many odd plotholes in Sailor Moon that I wouldn't be surprised if it was just something that the creators did so that they could have a picture together.
OR, remember that youma during the episode with the photographer who was possessed by Nephrite? That youma could take pictures of people. Of course those people would get sucked into the photos, but maybe with Zoisite and Kunzite, it's different.