Most thumbnail viewers, that i know, arrange the thumbnails left-right-top-down, like text. I think, this is reasonable.
MC presently arrages thumbnails top-down-left-right. Thanks!
Thumbnail view work as it does because it is built from the list mode. It is really the list mode with thumbnails instead.
Building a thumbnail view that worked that other way would require so much work that I do not even want to think about it.
But a Thumbnail detail mode are planed. It is build on Detail mode but with thumbnail (Top->Bottom) one thumb per line with size info and other info the the right of the image.
Mathias, thanks for your answers!