I remember when we were working on 'Young Learners' we learnt that they were encouraged when they produce something (booklets,story books etc.) at the end of the lesson. I think this tool is very good for children. I would want my students to make a book as a group. It would be for example at the end of the term. I would tell them that this is a project based lesson and they will produce an online-book. In order to do that, they will search for pictures and related information and by doing so, day by day they will become more interested in the given topic. They will learn something, hopefully.
Actually, I would not use this tool so much with my students because I think it is time-consuming. They may be more interested in the pictures and this may become a problem when they go away from the lesson point. I would introduce them bookr, but not let them use so much in the class.