Interesting that they have chosen flickr... so these could definitely be used for art purposes. These are remixable (collage! digital mashup! video!) and shareable by attribution (if I'm reading the cc correctly).
"An incredible archive of US Army medical photos and illustrations is being made available free under a Creative Commons Attribution license on Flickr by the National Museum of Health and Medicine:
This previously unreported archive at the National Museum of Health and Medicine in Washington, D.C., contains 500,000 scans of unique images so far, with another 225,000 set to be digitized this year."
..and here's the boingboing article about it.