I may be totally misunderstanding a post from swainzy in Cre8asite Forums, but maybe not. Swainzy is upset that she cannot change the number of results shown in Google Image Search, just like this person at the Google Web Search Help thread.
But what Swainzy added later seemed to imply to me that Google is testing Bing's infinite scroll feature, which continues to show you more and more pictures as you scroll the page.
G. may be over riding how many images you can see on one page but wow, it's much faster and the new page stays where you were on the last page. So if you are at the bottom, you don't have to see the image ads anymore.
Is Google copying Bing, who copied someone else?
I personally like the infinite scroll on Bing. Give it a try for red panda at Bing, just scroll and you will see what I mean.
Forum discussion at Cre8asite Forums.
Update: Google confirmed this test, a spokesperson told me:
We're continually testing new interfaces and features to enhance the user experience. What you describe below was one such test, which only a small percentage of users saw. We don't have any additional details to share at this time but I hope that helps. For more information on the experiments we run, please see: http://googleblog.blogspot.com/2006/04/this-is-test-this-is-only-test.html