To create a content template, the first thing to do, is work out what you would like as a template and customise it to fit your project. The file where these templates are stored is located in the default.xml file found here:
/plugins/arkeditor/xmltemplates/xmltemplates/templates/
You can quickly create a new templates by simply pasting your custom HTML code to the default.xml file as seen below.
<Template title="My title" image="myimage.gif">
<Description>My Description.</Description>
<Html> <![CDATA[
<p> My HTML code snippets</p>
]]> </Html>
</Template>
Then take a screenshot of your template, crop it down to 100 x 70 pixels and upload your new icon to same directory located here:
/plugins/arkeditor/xmltemplates/xmltemplates
Next, you will need to refresh your browsers cache files.
You will now have created, a content template plugin. You can view your changes, by checking the template plugin.