To enable thumbnails in Windows Explorer:
1. Go to Control Panel in the Start menu;
2a. If you use the Modern View click the Appearance and Personalization section and open Folder Options;
2b. If you use the Classic View double click Folder Options;
3. Browse to the View tab and uncheck Allways show icons, never thumbnails.
4. Save your settings by clicking OK!
I don’t know how to get the Slide Show function in Windows Server, maybe someone else knows?