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.
Confirmed. The feed is still not-quite-working (no new additions since Nov. of last year, even though there are newer wallpapers on the site), but that isn't due to anything we've done.
We definitely need that message--something on the order of "Fetching list..." or "One moment please..."
Actually it takes a 2-3 seconds on 3.5.13.2, too.
BTW: is there a way to show all available wallpapers?
Nik