DeviantArt has a lot of stock photos available for artists but the quality is pretty variable. You have to wade through of a lot of less than wonderful photos to find the good stuff. Here's a list of some great stock photo deviants I've found lately.
Those marked with a * contain tasteful artistic nudity which may make them unsuitable for viewing at work or school.
Mjranum-Stock* - Some of the most beautiful stock I've seen including some 360° flyarounds.
SenshiStock - Wonderful collection of figure photos, with the model in a leotard.
spiked-stock - Various poses in casual clothes.
wildchild-stock - Ethereal draped poses.
Elandria - Fantasy and historical costume.
Iardacil-stock - Fantasy poses and costumes.
gentlemansclubstock - Vintage nude photos.
Darknight-Stock* - Gothic guy and poses.
watchstock* - Nude male in classical life drawing poses.
Felixdeon* - Nude males.
Bit of Everything:
mizzd-stock - Fun collection of models in costumes.
lindowyn-stock - Mostly fantasy poses and costumes.
lockstock* - Great mix of stock.
LinzStock - Along with some good people stock there's some wonderful animal photos.
atistatplay - Really fun stuff, mostly from RenFaire and the like.
I also have a small DeviantArt stock account, not much there right now just some photos from the garden and my pets. Absolutely safe for work viewing. Noadi-Stock