So, this is where you choose the new file-level wizard (the description in the panel explains what you'll end up getting if you use this wizard—an HTML file and a Java source file).
And here's the first panel (and, thanks to the bottom panel—which seems to be a recent-ish feature that many NetBeans IDE wizards have, so that the user doesn't have to click 'Next' if there are only two panels—this is also the last panel in the wizard):
The lower part of the panel currently does nothing. Ultimately, a checked component will result in Java code being added to the Java source file and HTML tags (for rendering the component) in the HTML file.
In addition to the HTML file and Java source file (with some default code), currently the Wicket servlet is declared in web.xml when the above wizard is complete. Of course, I should move that part of the code to the project-level template, because the servlet should be declared only once—when the project is created (not every time a web page is created). But, this has been the most interesting part so far—learning how to use the J2EE DD API (especially see this usage page for some interesting examples) has been tricky (thanks for the help, Milan!) but, at the same time, quite a lot of fun. I'll add what I learnt about this API to the Wicket Project Template Module Tutorial soon...