There is a BETTER alternative Rated 3 out of 5 stars

This one doesn't have a ugly little icon in the context menu, and also requires no restart of Firefox to install.

https://addons.mozilla.org/en-US/firefox/addon/google-by-image-restartless/?src=search

cheers!!!

This review is for a previous version of the add-on (1.0.3.1-signed.1-signed).