Very interesting finds.
I know that fan projects or mods often use stock photos, but somehow I always thought that professional developing studios created their own artwork ...
Makes me wonder whether the "art deco" style of presentation was also chosen for economical reasons (not that much effort to filter existing stock photos in a way that it matches an art deco presentation, even if taken from very diverse sources).
Fan projects use stock photos because of lack of manpower, lack of design knowledge and fair use. But it's ok, they are mods, many game developers learn their trade through mods and eventually build themselves up to professional standards.
That Firaxis is using stock images is more than a lazyness, it's a liability. Of the hundreds of art assets within the game, unless ALL of them are public domain, or all of them have permision or were leased legaly, then Firaxis could be facing a few letters from a few lawyers.
I'm a graphic designer and I have not used stock images since my first year of college, because it's a potential liability. I know a lot of fellow designers do so, that's their thing. But I find it to be of poor ethics (not to mention the visual language ends up being all over the place, from comicbook-like quality to photorealistic).
My wife is a photographer, and while we are amused, she was pissed off to find that not only some of these images might have been used without asking for permision (we assume, as most of these are from the first few pages of google image search) but also that they were "drawified", often through the use of photoshop filters. As if that would make more dignifying.
And now more examples:
Trebuchet used as a visual reference (the boulder and rope part being the only difference)
Visual reference likely used for the Brute. It's cute that this was found on google under "brute". Still, some work done here, no liability (maybe framing and pose). Let the audience judge this one.
Donkey is a perfect match. TWICE. Still looking for the father and son and the woman. The father and son are likely 3 composite images: the bottom part holding the legs, the son and finnally the fathers face. The lady is likely just one image.