What image is used for folder thumbnails?

[redpaprika]

Hi!

I don't understand the logic what image is used for the folder thumbnail. It doesn't seemt to be the alphabetically first or last, not the newest or oldest, not the biggest.

For certain folders I want to use a specific image (with basically just the text "private" on it) as folder thumbnail, but i don't know what to change (name, size, date, exif-data,...) of the image to be taken as thumbnail image. I know that I can generally disable folder thumbnails, but that's not what I want. Is there any trick to force Xnview to use a specific image for the folder thumbnail?

[marsh]

I remember reading first files on hard disk (unsorted for speed). Someone correct if wrong.