Deleting blocked caused by thumb.db on Windows 2008 as a file server

Would you consider completely disabling thumbnail generation a valid option? That would certainly work. Though it comes at the cost of some usability.

Group policy User User \ Administrative Templates \ Windows Components \ Windows Explorer

Turns off the caching of thumbnails in hidden thumbs.db files.

This policy setting allows you to configure Windows Explorer to cache thumbnails of items residing in network folders in hidden thumbs.db files.

If you enable this policy setting, Windows Explorer does not create, read from, or write to thumbs.db files. If you disable or do not configure this policy setting, Windows Explorer creates, reads from, and writes to thumbs.db files.

https://superuser.com/questions/2345/how-can-i-suppress-those-annoying-thumbs-db-files-in-windows-vista-and-windows-7