Gamification, i.e. applying game elements in non-game contexts, is been increasingly used for designing systems and application elements to foster user engagement, enjoyment and support behavior change. Experts agree that, to be efficient, gamification strategies should be designed in a user-centric fashion. However, current user-centered design approaches in gamification primarily involve users during user research and iterative testing. In this paper, we describe an ideation approach for involving users in the conceptualization of gamification, making the gamification design process a more participatory activity, a process done with the user rather then for the user. Our results show that our method fostered participation without confining creativity. Participants were able to generate many ideas, several of them being “out of the box”.