Actually in HammerKit it is done the opposite way around. The link is a container into which you can add text or images. To do this:

1. Go to the Component Editor and open a component
2. Drag a Link element from the Element tray to the canvas. This will display the settings box.
3. Specify the component, file or web address that you would like the link to point to.
4. In the Text section at the bottom of the settings box, choose "Container Element" and click OK.
5. Now drag an image element inside the Link element. 
6. Click save and then preview your link to test it.