As someone who has used stock photos in a past job, I can appreciate the creative photographs some photographers see when they capture an image.
I always had something in mind when i was searching for stock photos, whether it was for a blog i wrote such as the following hyperlink or an article. The nose knows or does it
While i no longer work for this company it does provide an idea of how some of the pictures we take may be used.
In my opinion, signs are something that people look for to use in an advertisement. This next image shows a unique sign and hopefully a potential client finds useful.
Most stock photos are only limited by your imagination and it's likely that something you find interesting or envision in an ad or motivational poster or the like, a client would as well.