Google has confirmed the additional "date annotations" in a Google Web Search Help thread this morning.
If you search in Google Image Search for images that may have news related images, and if the images are fresh and picked up from Google - Google may add a label when they found the image. The label normally reads "X hours ago" or "X days ago" and is currently positioned at the bottom right corner of the image.
Here is a larger image of this:
Jeff from Google said "we're announcing a change which should make finding recent images a lot easier--Google Images with Date Annotations. Now, we'll add date annotations right to the thumbnails of images that were uploaded recently."
Pretty useful, don't you think?
Google has not yet announced this on their blog, I suspect they will on Friday afternoon or Sunday.
Forum discussion at Google Web Search Help.