NiftyImages
NiftyImages is a third party service that makes it easy to create personalised images and countdown timers for use within email.
There's support for all of the standard merge tags e.g. {?$contacts_first_name?} which can be added when creating the content within the Nifty control panel.
Using NiftyImages
Sign-up for an account with NiftyImages then follow their guide to creating personalised images. As part of that process you'll be given a direct link to the image you have created and you can then use that within an Email Template.
Using the drag & editor if you click on an image (or image placeholder) and then in the sidebar set the source to be 'Hosted or Dynamic Image' you can enter the NiftyImage URL directly.
To use a NiftyImage in coded Templates simply add the URL to the source attribute of an image tag and upload as normal.
For more info on how to create NiftyImages take a look at this video tutorial.