Very Nice Add-On Rated 5 out of 5 stars

I like the add on very much one for the possibility to add thumbnails by stating the number of rows and columns. This also seems to be the main purpose for the New Tab Tools Add-On even though it has the option to assign images from the internet or your computer's hard drive is a possibility. I have created thumbnails for most of my boxes, but it doesn't always keep them. From time to time it will replace my assigned image with an updated screenshot... I am not really sure why though. I wanted to write a review because I really like this Add-On because I was using pinned tabs for all those pages I wanted easy access to without having to open a bookmark menu or have a cluttered menu bar, etc. But still I wanted to bring it to the developer's attention because I am fairly certain he will improve upon it as time allows. Nice work Geoff and thanks.

This review is for a previous version of the add-on (3). 

Unfortunately in the current (release, beta) versions of Firefox there's no way to protect the thumbnails from Firefox overwriting them. In newer versions of Firefox the thumbnails stay put.