would be perfect with some additions: Rated 4 out of 5 stars

Very well done. I would love to see those additions:

1. Adding those image reverse search sites:

BYO Image Search Labée Inc.
http://labs.ideeinc.com/upload/

Cydral
http://www.cydral.com/
that has this extension:
https://addons.mozilla.org/en-US/firefox/addon/244885/

Yandexhttp://images.yandex.ru/
that has this extension:
https://addons.mozilla.org/en-US/firefox/addon/266838/

There is also this one which I didn't test because it's in Japanese...
https://addons.mozilla.org/en-US/firefox/addon/264495/

2. Maybe you can even add option to add customizable links to the list, for uploading images to more sites for reverse image search or other image manipulations!

3. Also, you might add the option to show the site's favicons in the context menu, like in the TinEye official extension and two of the others above:
https://addons.mozilla.org/en-US/firefox/addon/8922/

4. Finally, how about adding "Open All in Tabs" at the bottom of the sub menu, to search the image in all sites with a single click, simil to what the Organize Search Engines extension does:
https://addons.mozilla.org/en-US/firefox/addon/4565/

This review is for a previous version of the add-on (1.8.3.2).