Folder preview “suggests” folder is empty of pictures, but in fact there are pictures contained in subfolders. (Not in the top folder, yes).
Top Folder > Sub Folder (no images, just folders) > Subsubfolder(s) that contain images
Feature idea:
Randomly select previews from Subsubfolder(s) that show on the Top Folder’s preview. Could be extended in depth too to Subsubsubfolders or further down.
This will not “suggest” a folder has no images if in fact it has, in subfolder(s).
This will better preview your sorted collection in general.