You can create your own template or get a designer to do this for you if you do not wish to use a pre prepared template.
To create your own template click in the Kmail tab go to Templates and Create Blank Template.
This will take you to the editor. Enter a Template Name (for your reference) and Email Subject (that will be the subject header customers will see).
The top window is where you create your template using the tools much like you would in a word document and add images.
Click Save to view the email in the preview window. The kmail will be stored under My Templates and will also be listed under Templates on the home page.
For information on how to edit please see the Edit Kmail templates mini guide.