Photo shoots can take place quite some time before details of a set are finally decided on or the actual parts being available, or so I understand. If you look closely at the printing on the box, you may also find words saying something like this: "Contents may differ from those shown in the illustration", as this allows details changes to the set to be made, e.g. a change of colour of a piece or a change of design, to be made without having to reprint all the box.