Although there's an amazing guideline about stock images, which I helped to update recently on CRPhotomanipulation (https://www.deviantart.com/crphotomanipulation)
(which I highly recommend you have a look at)
I want to take another approach to this category.
I have been around devianART for 13 years now. Back then, the resources were quite limited, and some really talented people started working their asses off to provide us with amazing stock images.
They invested their time, their money into costumes, wigs, and so on.
And I really do want to mention some of the stock artists who are still around, and still kick ass at providing amazing stock images:
`faestock (https://www.deviantart.com/faestock) :icon