No, I just search for images on google. Some might be copyrighted so I might get into trouble. My argument will be Im a non profit organisation and the owner can support my cause by giving me rights to the image if they have a problem.
If you think you can run into legal issues, you could search for CC images.
Flickr has a filter in which you can find images you can legally use and even images for free public domain.
It is a good source for finding images you can safely use.