Cloud Video and Photos:
https://www.istockphoto.com/videos/cirrus-clouds?sort=mostpopular&offlinecontent=include&phrase=cirrus%20clouds (https://www.istockphoto.com/videos/cirrus-clouds?sort=mostpopular&offlinecontent=include&phrase=cirrus%20clouds)
https://www.istockphoto.com/videos/clouds?offlinecontent=include&phrase=clouds&sort=mostpopular (https://www.istockphoto.com/videos/clouds?offlinecontent=include&phrase=clouds&sort=mostpopular)
Noctilucent Clouds:
https://www.google.com/search?q=Noctilucent+Clouds (https://www.google.com/search?q=Noctilucent+Clouds)
We have a bunch of reference images on our pinterest page. https://www.pinterest.com/NWDAstore/boards/ (https://www.pinterest.com/NWDAstore/boards/) if anyone is interested have a look