The New York Public Library has released over 180,000 public domain images from its collection. Said collection of images is largely photos and artwork, but also include various sheet music, manuscripts, maps, and so forth. Since all of the material is under the public domain, it’s free for anyone to use. NPR has more on this collection release.
Of relevance to this blog, some of the materials are by and/or about African-Americans during the early- to mid-20th century. This includes photographs of various people going about their lives, as well as various types of artwork. A few examples are below.