Actually, the template which you choose on page creation is an item from section Pages -> Templates. Each Page Template has a .master page file associated to it. In addition to the master page you could add more controls to the content place holders and edit their properties. You could set the theme from there, add header controls and set other options.
We are also considering adding the default template feature as it would allow faster page creation. We cannot promise it will make it into the next release though.
the Telerik team