I have been sharing with people not to use images you find on the web for your website or e-mail (once I learned that myself). Images are property and they belong to someone. If you use them without the owner’s permission, you are going to get into trouble. Well, I recently bumped into someone who said, “If only you had told me that two years ago.” In setting up his website, he used many pictures. Only two of these had come from Google images. Unfortunately, he received a cease and desist order from the owner and, ultimately, had to pay a $5000 fine to settle the issue.
I know that it is hard but please take your own pictures, hire a photographer, or purchase from a reputable source. If you get your pictures from a source on the web, make sure to check the licensing and document your source should there ever be a question. A recent piece on this topic can be found at Sitepoint.