Have to be careful, we can’t allow any Getty images.
Didn't I read recently that Getty cried "Uncle" and decided to allow free use as long as a suitable credit is included?
But lots of luck with that, Getty! Images are everywhere, especially considering Twitter! From the above link:
It's a real risk for the company, since it's easy to screenshot the new versions if you want to snag an unlicensed version. But according to Craig Peters, a business development exec at Getty Images, that ship sailed long ago. "Look, if you want to get a Getty image today, you can find it without a watermark very simply," he says. "The way you do that is you go to one of our customer sites and you right-click. Or you go to Google Image search or Bing Image Search and you get it there. And that's what's happening… Our content was everywhere already."