The main aim of this study was to examine how different physical activity domains are represented on the official social media sites of Spanish universities, through a content analysis of the photographs. Our results show that the representation of different physical activity domains is not balanced. While the analysed images do promote a message of gender equality in sedentary and leisure time physical activity behaviour, pictures illustrating active commuting and disabled groups were under-represented. We conclude that Internet-based physical activity promotion in university settings must to be guided by the principles of "health-promoting universities" in the sense of promoting a comprehensive view on healthy behaviours in every action carried out with the university community, and in particular including diversity as a norm rather than the exception. Professionals should be aware of their responsibility in the design of the built online environment and their influence on the welfare of the university community.