Google Image Search lets you restrict the results using some content filters introduced in May 2007 directly from the standard interface. Until now, the options were available in the rarely-used advanced search page.
There are two kinds of filters:
* images from specialized search engines: news content shows images from Google News' index (news articles from the past 30 days)
* image analysis filters: Google uses face detection technology to find images that include faces and an interesting algorithm that finds photos.
I think the news content filter makes more sense as a Google News filter and it should be expanded to the entire News Archive. Microsoft's Live Search has three additional filters: illustrations, portraits, non-portraits that include faces, which are useful for some searches.