I have a specific idea on how to co-create something during the conference and get a sense of what co-creation is:

Together all Next participants could create something: a library, a city or perhaps an open book with a story displayed. It should be visible (build in cardboard or recycled materials) and growing throughout the conference. Along with the building we could create a story or a poem that tells the story about what happens in the library or city. Everybody should contribute to the work by building a small part and/or writing a sentence and the parts could be assembled by a professional artist or architect and a writer.