Churches Around the World is a blog that posts photos of the world's churches. It's tagline states that it is a "Photo Archive of Religious Buildings Around the World: Churches, Cathedrals, Chapels and Monasteries."
The countries represented here are vast and include Cuba, Estonia, Finland, Germany, Khazakhstan, Lithuania, Luxembourg, Portugal, Russia, Slovakia, Sweden and New York City.
The map website, Panoramio is also a good place to look for photos of church buildings all over the world. This website allows people to "tag" maps of places with photos they have taken. You can search this website by place and see what photos have been uploaded for that place. You can also search by keyword.