Using xencenter, we can create our own custom templates like create a vm based on existing templates, install OS, run sysprep and shutdown, then convert to template. Using this custom template we can deploy as many vms as we need and it has some OS in it. But if we want to create an empty template(skeleton template) without any OS, we can do it by this process:

1. create a vm using “Other install media” template in xencenter.
2. Now convert that vm into a template.
3. Create new vm with that template.

Now you have your own custom template(skeleton or empty template).