Most of the information on this page about finding images came from the LibGuide, Art, Art History, and Design by Visual Arts Librarian Marsha Stevenson; see it for more information on image searching.
Find illustrations in print sources by searching the ND Catalog. Often older books on costume or fashion (pre-1940) will have photographs of earlier clothing. Many of these pre-1940s book have been digitized and can be found on Hathi Trust through the ND Catalog.
For example, searching "costume United States history" retrieves the illustrated History of American Costume, 1607 - 1870, by Elisabeth McClellan, published in 1937 and available online on Hathi Trust.
Sometimes the captions identifying illustrations can be retrieved by searching Google Books.
In JSTOR, captions can be searched by changing the default dropdown from "Full-text" to "Caption."
To find depictions of a particular subject, the library catalog can be searched with a phrase such as "slaves in art."
Another option is to try a topic in the library catalog along with the words "pictorial works," e.g. search for "clothing pictorial works."
Frederic Schall, Paul et Virginie. 1795, Print, 418 x 486 mm. Kunstsammlungen der Veste Coburg. Available from: ARTstor, www.artstor.org (accessed March 23, 2016).