The default content for a new wiki page can be chosen from a list of page templates.
That list is generated from all the wiki pages having a name starting with PageTemplates/.
The initial content of a new page will simply be the content of the chosen template page, or a blank page if the special (blank page) entry is selected. When there are no wiki pages with the PageTemplates/ prefix, the initial content will always be the blank page and the list selector will not be shown (i.e. this matches the behavior we had up to now).
To create a new template, simply create a new page having a name starting with PageTemplates/.
(Hint: one could even create a !PageTemplates/Template for facilitating the creation of new templates!)
After the first template has been created, a drop-down selection box will automatically appear on any new wiki pages that are created. By default it is located on the right side of the 'Create this page' button. The default selection will be blank page, or !DefaultPage if !PageTemplates/DefaultPage exists.