There’s no formal blog post about this that we know of yet, just a tweet from Google’s Jeremy Hylton announcing that images are now showing up in Google’s real-time search results.
Actually, you have to specifically request to include images with your results. After doing a search for “lunch” and clicking to see Updates from the left options menu, you then have to click the new “Updates with images” to see results like this.
Note that the focus here is still on the update; this is not a real-time image search tool. If you’re looking for that, here are several options:
Photo upload services such as TwitPic.com, yfrog.com and others also serve as real-time image search engines to some degree, but those are limited to searching only the photos uploaded on their own platforms.