Rated 3 out of 5 stars

Beautiful Idea! However, most of it ends up below the tab line in the lighter, grayed out area, spoiling the effect. Also the words are blurry, especially in the top left while the caption near the animal is partially cut of at the top.

Hi, many thanks for taking the time to review, especially as it's my first review since I started creating these 7 months ago; I was beginning to think I'd never get one!
I accept your criticisms, but suspect you have upgraded to Firefox Quantum, aka Firefox 57. I did the same, but within half an hour I had uninstalled it and reverted back to Firefox 56. To me the whole point of Firefox was the amount of customisation it allowed you, but the new Firefox has gone the way of all browsers and software companies in general, making you see what they want you to see in the way that they want you to see it!
With the new one I found that the tools I used for my customisation, most notably Classic Theme Restorer, no longer had any impact and there was hardly anything I could change any more. This was particularly galling for me as a theme creator who, admittedly, always designs them so that they work well in my own highly personalised Firefox, allowing me to adjust the number of rows of additional empty toolbars and making the address bar appear only when hovered over, to name but two of very many.
I had hoped to be able to include a screenshot to show you how it looks on my machine in this reply, but that function doesn't seem to be allowed. Of course, if you are really interested to find out I could always e-mail it to you!
Thanks once again for taking the time to review, and I'm very sorry that it doesn't work so well for you as it does for me.