Google Instant on image search results, an experimental feature is now available. After you enable "Instant on Images", Google will start to autocomplete your queries and show image results before you finish entering the query.
Unfortunately, there are some limitations with this feature at this time atleast. "Search by Image will not work if you opt into this experiment. Also, Instant on Images is available only if you already have Instant on Web. Finally, this experiment is enabled only for the Images search result page, not on the Google Images home page."
With Instant on Images you can:
- Faster Searches: By predicting your search and showing results before you finish typing, Google Instant can save 2-5 seconds per search.
- Smarter Predictions: Even when you don't know exactly what you're looking for, predictions help guide your search. The top prediction is shown in grey text directly in the search box, so you can stop typing as soon as you see what you need.
- Instant Image Results: Until now, you had to type a full search term, hit return, and wait for the right results. Now, images appear instantly as you type, helping you see where you're headed, every step of the way.
You can try this feature without joining Google's experiment: just append &esrch=ImagesInstant::PublicOptIn to an Image Search URL, like this or bookmark this page.
[Source:Google Experimental search]