For non-copyrighted stuff I think the best bet is seaching various forums for amateur pics. There's some pretty good ones around (I've used a lot of them as sources when researching gubbins for the EW MBT project). There's no real copyright on that sort of pics AFAIK but of course it would be polite to drop the user a mail and ask for permission to use them first.
I don't know if image databases like Flickr or
http://sxc.hu/ might have something for you.
For the printed stuff getting permissions and avoiding copyright is a must. For net based stuff it is more likely you'll just recieve a notification to remove the pics if there's any issues.