Take a look at Topimagesites at http://topimagesites.com
Topimagesites compares and reviews all the top stock image websites. You can compare prices and features, but you can also search all these stock image websites simultaneously - for any image.
Search for e.g. "bridge" and you will have each of these stock image websites show you their best images for this term. This allows you to search more than 500 million images with the click of a mouse (or touch of a screen).
We have also added the special offers, discounts and free trials that these agencies provides on a separate page.
Feel free to take a look.