Recall from @Nicolas_Raoul : Let's say Joe is in the train with 30 minutes to kill, and he has already uploaded all of his interesting pictures. Joe could start playing a mobile game, but he prefers doing something for the greater good.
As the first step our gamification plans, we want to implement review option for this hackathon. Related discussion: https://github.com/commons-app/apps-android-commons/issues/780