You probably know that Wikipedia's best articles become Featured Articles. But did you know that a similar process exists for images? Go to Featured Picture Candidates to help judge which images are both attractive and valuable to Wikipedia.
Of course, the best can be found on featured pictures. Many of these photos are taken by Wikipedians. If you are a photographer, you can add yourself to the list, or encourage others by nominating great photos you come across. Feel free to use featured pictures in your own works (according to the terms on the image description page).