Thumbnails can be either on or off for everything. But you can do some tweaking so toggling thumbnails on and off becomes easier from any folder.
Here's how to add "Toggle thumbnails" to background context menu:You can use VBScript and tweak the registry to add a command to toggle thumbnails from the context menu. Download this ZIP file:
http://www.classicshell.net/forum/download/file.php?id=1299 and extract
ToggleThumbs.vbs to your
C:\Windows folder. Then double click to merge ToggleThumbs.reg into the Registry. You will get a context menu item called "Toggle thumbnails" when you right click the empty background of a folder or a Library.
How to add Classic Explorer toolbar button to toggle thumbnails:Instead of merging the REG file for getting a context menu, you can also copy the above
ToggleThumbs VBS file to C:\Windows and then create a custom toolbar button on the Classic Explorer toolbar whose command is:
wscript.exe "%WinDir%\togglethumbs.vbs"