Stunning.

              "Courtesy NASA/JPL-Caltech."

So, in addition to Creative Commons being a great resource for finding images (whose creators have waived certain copyright rights for other uses), today I stumbled into Wikimedia Commons.  Launched about 3 years after Creative Commons, it's somewhat similar, though the rules for entering an image (or other media file) are slightly different.  

   Taken by Mila Zinkova. 

In any event, it's got links to some remarkable photos.  

From the Detroit Publishing Company Collection at LOC. (Though this copy may be digitally enhanced.)

  From the Edward S. Curtis Collection at LOC.