The Prints and Photographs Online Catalog (PPOC) of the Library of Congress includes some photos and drawings of historic churches. The Historic American Buildings Survey produced many drawings and some photos of churches, and I found some rarities, e.g., drawings of the Marion, Mass., Universalist church. There are also many glass negatives from the Detroit Publishing Co., c.1900-1910, including quite a few churches. Great search engine allows easy searching; hi-res digital files for downloading.