[ramshorns]

For these images, a lot of the legal issues would be simpler and fair use wouldn't be necessary, since they're all CC-BY.

[Smerity]

Not necessarily - they're listed as CC-BY on Flickr but that doesn't necessarily make it true. Specifically the user may not have authority to give out such copyright (as I assume for any case where the user "accidentally" set it to CC-BY they can't retract?)

Google included specific legalese on this very issue. See https://news.ycombinator.com/item?id=12616012