The Digital Humanities project Phototrails [phototrails.net], a collaboration by the Department of History of Art and Architecture (University of Pittsburgh), the Software Studies Initiative (California Institute for Telecommunication and Information) and The Graduate Center (City University of New York), uses various visualization techniques to explore the visual patterns, dynamics and structures in user-generated photos from online services like Instagram.
Basically, the visualizations are based on scaling and spatially organizing a massive amount of photos by a combination of attributes. Each technique highlights different aspects of the data: the "Radial" maps 2 data attributes (e.g. upload date, location) to the angle and the radius of circle. "Montage" consist of a grid-like structure that is organized according to time (i.e. upload date) or visual attributes (e.g. hue, contrast, etc.). "Photoplot" is a scatterplot, but uses individual images instead of plotting individual points. "Points and Lines" traces the locations of photos over time on a map.
Alternatively, one can explore the 'visual rhythms' of photos by city.