The demo images are licensed as United States government work:
https://www.usa.gov/government-works

The image files were obtained on Jan 13, 2018 from the following
URLs.

16004479832_a748d55f21_k.jpg
https://www.flickr.com/photos/archivesnews/16004479832

18124840932_e42b3e377c_k.jpg
https://www.flickr.com/photos/usnavy/18124840932

33887522274_eebd074106_k.jpg
https://www.flickr.com/photos/usaid_pakistan/33887522274

15673749081_767a7fa63a_k.jpg
https://www.flickr.com/photos/usnavy/15673749081

34501842524_3c858b3080_k.jpg
https://www.flickr.com/photos/departmentofenergy/34501842524

24274813513_0cfd2ce6d0_k.jpg
https://www.flickr.com/photos/dhsgov/24274813513

19064748793_bb942deea1_k.jpg
https://www.flickr.com/photos/statephotos/19064748793

33823288584_1d21cf0a26_k.jpg
https://www.flickr.com/photos/cbpphotos/33823288584

17790319373_bd19b24cfc_k.jpg
https://www.flickr.com/photos/secdef/17790319373