Brilliant! Rated 5 out of 5 stars
This extension is fantastic!
The newtab with thumbnails that FF added since version 13 was an excellent improvement, but it is frankly boring. Adding a background image makes it much more visually attractive.
So, using your extension, the background photo is a different one each time - you have with a simple solution made Firefox more beautiful.
A suggestion: Maybe you can integrate all your background setting extensions in just one (the shuffler one is the obvious choice). Just to keep everything tidy.
Anyway, great work! Congratulations!
First of all, Thanks for your review and the nice words :-)
Regarding your suggestion, these add-ons are designed on a very lightweight fashion (ie, 1-2 KB) and therefore it shouldn't cause any real impact to your browsing experience if you install several of them. Maybe if you install 70 of them the startup overhead would be then the same as of some known extensions such as AdBlock or NoScript. However, i do not refuse the possibility to create another add-on (or upgrading this one) in the future to include the most used "newtab background"-based add-ons.