I don't really believe that you can if it is copyright'd... trying looking for GPL or CreativeCommons licensed photos.
Speaking as a photographer... and not a lawyer... If I can recognize anything about an image originating from my photo... then it is copyright infringement and I have every legal right to protect the use of my image. A photograph is copyrighted as soon as the photographer's original idea is produced in any tangible form and does not need to be marked as copyrighted (tho highly recommended). If you care to read this from the photographer's perspective... there is a guide posted here: Copyright Guide for Photographers
Thanks I just needed some small pics for a site. I found what I needed but pics did not have any info. Just seeing what is OK and what is not. Mike