Awesome!
Fast, minimalist, feature-rich and truly deserving of the term "fully customisable".

Edit: Unfortunately, uploading a custom image to Bonjourr doesn't seem to work when firefox is said to its strictest privacy settings. Specifically setting the History setting to no history / permanent private browsing seems to be the issue.
Though I am not sure whether this is a limitatation of the setting or an oversight of the plug-in.

This extension offers a minimalistic somewhat customizable startpage that looks absolutely stunning.

Also this is the only extension that I found that respects your privacy as it only wants access to your location, which you can even disable I think, instead of access to your whole browsers data like all the others.

Still I only give 4 out of 5 stars as the search bar is useless to me in its current state as it's not automatically focused when opening a new tab.