Rated 4 out of 5 stars

Customizing tile images didn't work, error console message:
ReferenceError: PageThumbsStorage is not defined
Source: chrome://newtabtools/content/newTab.js
Line: 89

This review is for a previous version of the add-on (2). 

Oh damn, PageThumbsStorage didn't exist until Firefox 16. I will find a way to fix that.