I finally got all the pages in the site using Paul Wilson's MasterPages implementation. I've also changed my mind about needing to skin the site header separately. It will be better to break the site header control up into its constituent components and make them into their own controls and then position them within the MasterPage template. This will allow a great deal of flexibility in terms of design and make the design work very easy to understand for anyone who understands HTML. The templates are just .ascx files with markup. I plan to display them in a dropdown on the admin page. You would simply create a new one and drop it into a folder to add a skin. Of course you would have to include any supporting images and style sheets.