Theses collections at the the New York Library Digital Collection are useful if you need to find a head shot for an NPC. Many of them are still in copyright but still a good resource for personal use.
The Friedman-Abeles Photograph Collection head shots of actors from productions mostly from Broadway and off-Broadway shows between 1954-1970.
The Vandamm theatrical photographs runs from 1900-1957 and doesn’t have as many as the Friedman-Abeles Photograph Collection.
Kenn Duncan Photograph Archive runs from 1960-1986.