After many hours of research and shifting through the websites, I've come up with four of them that I highly recommend (plus one obvious one many people forget about). These sites have excellent quality images, primarily photographs (not just tacky clip art) and their generous reproduction rights make them free in cost and guilt-free for churches to use.
This video not only gives you the location of the sites, but it goes to the sites and shows you a brief, visual tour of them.
Below are PDFs of both the notes for the video and a list of websites for free clip art and copyright information. Click on each image to download the PDF.