Jennifer Laycock writes a great article on how using images can boost traffic.
"While vertical search is still in its infancy, the integration of vertical results through Google Universal and Ask 3D are allowing sites to draw more and more visitors from specialty indexes. One of the vertical search indexed that is becoming more and more popular is imagine search. Unfortunately, many small businesses are overlooking traffic opportunities by not optimizing the images on their sites.
You'll note there are three images from the Google image database showing up at the top of the listings. Since I'm hunting for ideas for my son's first birthday cake, I'm far more likely to click on images than on the standard text results. In fact, I'd wager there are quite a few keyword phrases that are likely to send a fair amount of image search traffic."