>> Hi nik,
>> could you post a screenshot of what the "Get New Wallpapers" window looks like on 3.5.13.2? That would be helpful for when we will work >on fixing the problem, at least we can get an idea of what the result has to be.
>
> here you are :-)

Part 1:

Thanks Nik, much appreciated.
I have filed bug report 2093 about it and added the bug to the v14.0.0 release list, being a considerable regression from 3.5.13.2.
The screenshot has been attached to the bug report.

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Part 2:

Actually after clicking the button and leaving the empty window open for a while, the wallpaper list gets populated, as in the screenshot posted by Nik. So it looks like we just need to add some kind of message to the window when it first open, advising the user to wait for a few seconds.

Cheers
  Michele