Tool for Finding High-Quality Images

Google image will find you lots of image results, but they may not get great results. Serendip-o-matic.org can increase your odds by hitting up the right sources. Enter some keywords or even a whole paragraph, and you'll get image results from repositories like Digital Public Library of America (DPLA), Europeana, Flickr Commons and the National Library of Australia's Trove.

For example, a search for "Electric Guitar" brought up a bunch of images from the Smithsonian.