Is there a way to prevent Thumbs.db from being created, on the SERVER side?

There's not really a good way to control this "server side" with any mechanism other than Group Policy (which, ultimately, is just making a setting in the client computers' registries).

Have a look at the setting "Turn off caching of thumbnail pictures" under "Windows Explorer" under "Windows Components" under "Administrative Templates" under the "User Configuration" section of a Group Policy Object.

With Windows Server 2003 and newer, the File Server Resource Manager can be used to enforce policy about the kind of files saved into a network share.

1. Use the Server Manager to add the File Server Resource Manager, one of the role services available when File Services is installed.
2. Open the File Server Resource Manager administrative tool.
3. Define a new File Group that includes "Thumbs.db"
4. Define a new custom File Screen to use active screening, and select your custom file group for Thumbs.db files. You may optionally choose to send a warning to the event log each time a file is blocked.
5. Use a Windows client to browse some images on the share, and verify that Thumbs.db is no longer created.
6. If you enabled event logging, it will show up as a warning event 8215 in the server's Application log from source "SRMSVC".

This feature should work on 'older' environments (XP, Server 2003) To turn this feature off, do the following:

1) Open My Computer 2) Click on Tools 3) Click on Folder Options 4) Click on the View Tab 5) Place a check in the option "Do not cache thumbnails" 6) Click Ok 7) Close My Computer

This should work in 'newer' environments (W7) gpedit.msc User Configuration | Administrative Templates | Windows Components | Windows Explorer Double Click “Turn off the caching of thumbnails in hidden thumbs.db files” (3rd item on right) Source: http://www.technoleros.com/turn-off-caching-of-windows-7-thumbnails-in-hidden-thumbs-db-files/