WindowShopper lets you use visual search to find shoes, handbags, jewelry, home decor or any other product! Click on products images in any site to also compare prices, find deals, and get coupons.
Here is a little more about the add-on from the developers:
After you download and install WindowShopper, you will see a “See Similar” icon appear next to product images in any site. Just click on the icon and the WindowShopper window will appear, presenting deals and visually similar products from more than 50,000 online stores. This Service may also present deals, coupons and/or other services on relevant product pages. In some cases by clicking on a presented offer, the user will be redirected to the partner’s (aka advertiser’s) site via affiliate cookies.
Want to learn more? You can get more information about this add-on from the Firefox Add-ons website.