Finding images online, as well as in print,is important in the design disciplines. This guide will help identify resources for finding images via the Web using both search engines and dedicated collections of images related to architecture, landscape architecture, art and design, from both contemporary and historical perspectives.
A good place to start learning about finding and using images, whether in print or online, is Pretty Pictures: An Introduction to Image Research Methodology from Yale University Libraries.
Pretty Pictures provides a fairly quick yet comprehensive overview of image use for research.