A single Getty image could cost you $100+. I'm not sure how a blog can have 10s of thousands of unmarked Getty images. If they were to buy all these images it would cost of 100s of thousands of dollars. What I have seen blogs do is append a footer beneath the images and cite the source and link back to the licensed Getty image.
Is it okay to use licensed Getty image on your blog (for web publishing only. Not commercial use) without buying and just credit them in the footer?
Webdev, I can't answer your specific question, but I'd strongly recommend you contact Getty and check on their licensing terms.
They are hot on enforcing their copyright, as soon as they spot an infringement their legal team send you demands at a penalty cost.
Over the years we have been caught by them a couple of times, in fact we heard from them again just last month over an image displayed on an advertisers banner - we got out of that one!!
Just don't use images they have copyright on. As a starting affiliate you don't want to spend your limited financial resources on buying images if you can get them for free on google!
If you are using them for commercial purposes especially, I would be very careful ....