The National Archives is a great source for Native American photos because it collects documents from more than a dozen government agencies. The National Museum of the American Indian also hosts a searchable online database that includes photo collections of many different tribes.
The National Archives' collection of Native American photos is organized by category, making it easy to find specific scenes from Native American life. The online collection is small but well-curated.
The National Museum of the American Indian hosts a more extensive collection of photos. Users can sort the Native American photos on the museum site by category as well as by region in the United States, so it is easier to find photos of specific tribes.