iStock

iStock (by Getty Images) is a fiercely pragmatic, deeply engineered leviathan that mathematically attacked the "Premium Microstock" sector. While Getty focuses on $500 exclusive editorial shots, iStock engineered a terrifyingly efficient, highly curated royalty-free engine. It is the absolute weapon of choice for mid-market creative agencies who mathematically demand the aesthetic quality and legal safety of Getty Images, but physically require a high-volume, credit-based subscription model.