Three months of server transaction logs containing complete clickstream data for an image collection digital library were analysed for usage patterns to better understand user searching and browsing behaviour in this environment. Eleven types of user actions were identified from the log content. The study is novel in its combined analytical techniques and use of clickstream data from an image-based digital library. Three analytical techniques were used to analyse the data: (a) network analysis to better understand the relationship between sequential actions; (b) sequential pattern mining to identify frequent action sequences; and (c) k-means cluster analysis to identify groups of session patterns. The analysis revealed strong ties between several pairs of actions, relatively short pattern sequences that frequently duplicate previous actions and largely uniform session behaviour with little individual item browsing within sessions, indicating users are primarily engaged in purposeful and directed searching. Developers of image-based digital libraries should consider design features that support rapid browsing.