Requirements Engineering (RE) is a decision-centric activity which is highly data-intensive. The results of this process are known to have key impact on the results of the project. As known from the experience in other fields and disciplines, visualization can potentially provide more insights into data, information and knowledge studied. While research in the area of information visualization and its application to software engineering has rapidly increased over the last decade, there is only a limited amount of studies addressing the usage and impact of visualization techniques for RE activities. In this paper, we report on the results of a Systematic Literature Review (SLR) related to RE visualization. Extending the established SLR process by the usage of grounded theory for the encoding of papers, we synthesize 18 usage patterns. Even though there are punctual applications, there is a clear deficit on a holistic perspective across the different RE activities. As another conclusion, we derive the clear need for more research on visualization support in particular for tackling requirements uncertainty, requirements verification, and modeling, as well as non-functional requirements (NFRs).