Sixty-eight young people contributed to a Design Thinking Challenge created to elicit a better understanding of their electronic image-sharing experiences, the helpful and harmful consequences of image-sharing to adolescent mental health and safety, and promising interventions that allow young people to make more positive decisions and minimize their risks when sharing images through electronic devices. Through this collaborative group-based process, each co-design group engaged in a four-phase process to discover, define, develop, and deliver an intervention that took the form of a paper-based mobile app prototype. Young people reported that they need information and advice to support their and others' online decision making, help making situational decision-making skills for managing online interactions, and means to control information and images that can be accessed and distributed. Detailed app features that they required to address their decision-making needs are also discussed. These app intervention features highlight what young people need to make better-informed decisions when communicating through images electronically.