1. Enable Developer Tools
2. Create Your Background and Customization File
3. Lock it down. (Enable Drawing Explorer)
4. Right click on the file name (C:\Users\etc...) and click "Protect Document" and then pick "Backgrounds". This is the Microsoft recommended method: http://goo.gl/PxS9EC
5. Before you save the document as a template. Make sure that you open one page and select background.
6. Save and close. Your now good to go.