How can i add SMB Directorys

SMB directories are not supported by cover-thumbnailer and there is no plan for support them yet, sorry :(

Please correct me if I am wrong but isn't the gvfs-fuse-daemon with the "$HOME/.gvfs" directory made exactly for those cases?

If I connect with nautilus to a SMB share the share is automounted to "$HOME/.gvfs/$share on $server/".
There I can access anything by command line tools and run every non-smb-aware tool in a transparent fashion.
So I'd think that Cover Thumbnailer should be able to access those files and directories too without too
much knowledge of the smb schema.

It just needs the logic to translate url's with
smb://user@server/share/path/file.ext
to
file:/$HOME/.gvfs/share on server/path/file.ext

I don't know if the nautilus plugin api exposes the translation methods, but they are sure there
as nautilus uses them all the time when handing non-gnome applications like mplayer a non-local file
to play.

Here's a blog post about it: http://davidz25.blogspot.com/2008/10/getting-gvfs-and-fuse-right.html

There's a whole lot more than just SMB and if the plugin api does the translation, it might be
a couple lines of code and Cover Thumbnailer could support DAV, FTP, obexftp and so on.

Hello, it is maybe just a disabled option in nautilus (Edition → Preferences → Preview) ?
(or nautilus sends an smb:// address to the thumbnailer... i need to check but i have not the time now)