Free public sources for photographs. Some sites have a mix of free and fee, be sure to check restrictions (if any) when using. When using media, please keep in mind Copyright and Fair Use issues (provided by MIT Libraries).
Which looks better to you? I think most will agree the real photograph. There are a wide variety of free online images to choose from so using clip art can seem outdated and unprofessional. Look on this page to find a list of websites and search engines to help you find free images online.