If you are looking for collections of imagery, video, and audio resources for the National Aeronautics and Space Administration (NASA) and for U.S. military units, here is a list of places to look.

NASA Image Collections

• https://www.nasa.gov/multimedia/imagegallery/index.html [you should provide credit to NASA for any image used]
• https://www.dvidshub.net/unit/NASA#.Vwu_9D-NA-8

Defense Video Imagery and Distribution System (DVIDS)

The Defense Video Imagery and Distribution System (DVIDS) is a state-of-the-art, 24/7 operation that provides a timely, accurate and reliable connection between the media around the world and the military serving worldwide. The DVIDS mission is to serve as a turnkey operation that facilitates requests for Public Affairs video, audio, still imagery and print products; coordinates interviews with soldiers and commanders in a combat zone and provides an archive for ongoing operations in Iraq, Afghanistan, Kuwait, Qatar and Bahrain.

This site contains imagery, video, podcasts, webcasts, and interviews for current and archival material for all military branches and units as well as all civilian units. A few pages you may find useful are

• Military and Civilian Units page:
  https://www.dvidshub.net/unit#.Vwu55z-NA-8
• Search Civilian Content: https://www.dvidshub.net/branch/Civilian#.Vwu8sD-NA-8
• Journalists Portfolios: https://www.dvidshub.net/portfolio#.Vwu9Vj-NA-8