be careful. i work for two churches and assumed some local pictures i found on google were 'public domain' or whatever you call it. i got a very angry email from the photographer showing me her blog and demanding that they be removed. someone had shared them, someone else re-shared them and her watermark did not appear nor credit. i don't know how to remove such a thing ... but it wasn't there on the copies i found.
in any case, never again for me!
i now tell everyone who submits things that we can only use photos they took or that they can show permission from the photographer to use. also, we have to have permission of folks in random pics which is a pain and sometimes we can't get.
i send out email news via vertical response and the irony is they have something like 75,000 images i can use with no worries. so using a random pic from google is unnecessary and not worth the worry. also, there is a source called morguefile that has a free photo section.
one of my bosses just recently sent me a flyer she was creating with images she found on google!! i had to go through the whole photo rule thing with her, (one pic i was able to trace to a blog and the artist said it was her copyrighted work she wanted payment to use). we ended up using some images from morguefile.