Nice, useful and flexable addon Noté 5 sur 5 étoiles
But there are few things that is worth to add.
1. Ability to add a site/url directly from this site via menuitem or button.
2. The NewTabPlus allows to edit the urls, logo etc. but it is not described clearly. Finally I found how to do this, but I think it is worth to add the explanation in this page
3. The addon allows to choose a wallpaper. It is great! But it would be better to give to user the ability to define the list of wallpapers and the actual background can be chosen randomly from this list