Philipp over at Google Blogoscoped points out that Google is testing placing few thumbnail images from their image database at the top of web search results pages. I tried a few searches but wasn't able to see any examples. Luckily, the GB post also includes a screen capture.
Btw, embedding a few thumbnail images directly onto a page of web results is not a new idea. Ask Jeeves has done this (if the query indicates the searcher is looking for images) for almost two years. Here are a couple of examples from AJ:
+ images elephants
+ pictures golden gate bridge