When we migrated to the new site framework a little over a week ago, we also changed the email ad format. Under the old system, it went from a text link ad at the bottom of the email to a full 468x60 banner at the top of the email. This also means you can use an image banner in email ads now. How do they perform? In the first week of statistics, they had a 242% higher click-through ratio than normal banner ads on the site. Here's an example of the placement: