1.) Spend some additional time brainstorming keywords and search terms based on the subject's life and/or significant political/historical events.
2.) Use subject headings or descriptors to help generate search terms.
3.) When you find a good article, look at its References or Works Cited list. That will often lead you to other useful sources.
Trial for Witchcraft-New England, 1692. transparency, collodion on glass, ca.1885. C.W. Briggs Company, George Eastman House. ArtStor Digital Library, lib-proxy.sunywcc.edu/login?url=http:www.artstor.org. Accessed on 20 Sept. 2016.
These sites are well-researched, but not of "scholarly" caliber.