Upload a thumbnail image from the Image Library
Note: Images must be JPG and will be inserted at the thumbnail size of 120 x 80 pixels. Files can be no larger than 1.562 MB.
Click Email > Stationery.
Click Create a New Stationery.
Click Thumbnail in the left-hand navigation pane.
Click Search the Image Library to open the list of images in your library.
Click the Select icon to for the appropriate image. The Stationery configuration page displays.
Click Next. The Publish Stationery page displays.