I prefer using just one thumbnail for a folder. This usually means the first image in the folder will be the thumbnail.
However it would be better if I can prioritize certain file names to be that thumbnail.
For example, there could be folder with a "front_cover.jpg" and a "back_cover.jpg". Ideally "front_cover.jpg" should be used for the thumbnail but because of the sorting, "back_cover.jpg" will be used since B is before F.
The only way around this is to rename the file to like "001_front.jpg" which now is out of place with the other file names in the folder. Or make a copy of the file.
It would be great if we can have a user defined priority list for the thumbnail creation.
Priority Files for Folder Thumbnail
Moderators: XnTriq, helmut, xnview
Re: Priority Files for Folder Thumbnail
Or... you could simply duplicate (copy/paste) your favourite picture and rename it as Folder.ext (jpg|png|whatever).