Images are a valuable resource for the study of technology in a historical context. These may take the form of photographs, technical drawings, maps, prints or paintings. The Internet provides a huge number of sources for these images, here are but a few.
Image Library of the British National Archives "The image library provides high-resolution digitised scans and photographic prints of The National Archives' images for commercial publication, display, broadcast and merchandise."
Scientific American Past
A collection of thousands of cover scans from the period between 1870 to 1939 and a growing collection of index scans from the same period.
Artcyclopedia
A searchable database of artists and works with links to the collections that possess (and post images ) of them.
Artchive
A basic database of overviews of major artists and their works with highlight images.
ArtSTOR
This database of images for scholarly research requires the user to be associated with one of the nearly 1,200 educational institutions that subscribe to the service.
Olga's Gallery
This site claims to be "one of the largest and most comprehensive collections" of artistic works on-line.
New york Public Library Digital Gallery
Extensive searchable collection of images organized by original collection (many of which are subject specific including technological topics) as well as by subject.
Images of East Asia at Harvard
A finding guide for the image collections at Harvard College Library. This page includes links to other image collections at Harvard.
Southeast Asian Images and Texts
The gateway to the digital collection of Southeast Asian resources at the University of Wisconsin.
The Library of Congress: Map Collections The starting point for searching the Library's map collection which includes maps from ancient to modern times from around the world, as well as city-views and an entire section transportation and communications maps.