We’re already in the process of organising merchandise:
As for the other stuff you’ve suggested, that will be a bit harder, since for a photo we have to try and get all the devs to take a photo, them to sign it and figure out a way to duplicate that and have it for sale (with worldwide shipping). In regards to a book, we will have to write it, figure out graphic design, and find a publisher who can do Print on Demand.