You can take customizing your Magento transactional e-mail templates even further by adding static blocks to the templates.
Firstly, you will need to create a static block you wish to insert into your Magento e-mail template. Navigate to CMS | Static Blocks and click on the Add New Block button at the top-right corner of the screen.
Provide Block Title and Identifier (the example uses email_ as a prefix to help you know where the block is used), as shown in the following screenshot:
Use the Content field to add content you would like to appear within the e-mail template itself. Once you're finished, click on the Save Block button at the top-right corner of the screen.