Valerie Harris and Peter Hepburn have published "Trends in Image Use by Historians and the Implications for Librarians and Archivists" in the latest issue of College & Research Libraries.
Here's an excerpt:
For years, libraries have offered reproduction services to users, with historians being the core audience. More recently, archives and special collections have developed digitization programs to make primary sources widely available through the Internet. The authors tracked image use from 2000 through 2009 in journals from the discipline of history to discover whether use of images has increased with the growing availability of digital images through libraries, or from social media sites such as Flickr. The study discusses the results, which show no increase in the inclusion of images in the literature, and the implications for librarians and archivists.