In response to a query, here are some websites where you can search for religious art online. Most of them make available historical images for any use. Some have restricted use - such as online viewing but not download - hence you can share the link or provide a device for people to view the art. Feel free to notify me of additional sites.
Vanderbilt University Library
Web Gallery of Art
Methodist Art Collection (UK)
Metropolitan Museum of Art - Free Images - go to page and select "Open Access Artworks"
National Gallery of Art
Smithsonian Open Access
Art Institute of Chicago
I'd also recommend ArtWay as a great portal to explore art and religion.
You can also search here for photos that people have taken of public art pieces.
These are all listed on my page Multimedia and Design Resources - listed right.
Image: ALTDORFER, Albrecht, Christ on the Cross between Mary and St John, c. 1512
Limewood, 102 x 116 cm
Source: Web Gallery of Art