I posted a kingdom here, using the card image button to show images, and the images wouldn't show for any card that has a space in its name.
EDIT: I found a workaround which may help you to find the bug: When I capitalized Hunting_Party, Horn_of_Plenty, and Hunting_Grounds, then the images showed correctly. (It took me two tries for Horn of plenty because I tried 'Horn_Of_Plenty' first.)
Also, how do you use the kingdom button in the fds plugin?
It's set up for capitalization to matter, though that's probably not ideal; because why should it? I think I can change that easily. Can't say why capitalization only mattered for multi-word cards; thought it would be the same for all.
For the Kingdom button, just list out all the cards with a comma (and a space after the comma) between each one. Like this (should stay as a list because the extension isn't installed where I'm posting from):
[kingdom]Hunting Party, Chapel, Scout, Laboratory[/kingdom]