Using Firefox Persona images as Background in Fast Dial

I have been asked about the feasability of using Persona images as Fast Dial Background

How can I get the Themes picture as background in FD?

There is an obvious immediate problem with this idea
The size of the persona images is 3000px wide x 200px high

This is not really the shape of the fast dial background.

You would have to decide if you wanted to tile these images as background or find a large version of the background and use part of it.

please see here and here

Perhaps try as a test saving this persona image to your PC and then loading as a background image into fast dial: (click on image to expand)

Let us first see if you can see the image.
Best to tile the background.
You should then see a background made up of strips.

Once you have got that one working, you can play around...

(I have tested with this image.
It does work fine in tiled mode)

I thought I could see that when choosing transparent in FDs preferences. But this only gives me a white background. What am I doing wrong?

the background colour only shows when there is no image.

If you have a small image loaded as background in centered mode, you may not see it easily unless you go into tiled mode.