There is a way to do this without editing the HTML. To add an image on a new line, while keeping it a part of an existing list item, use Shift + Enter. This will move the cursor to a new line while still staying part of the existing list item. This works in the editor used in version 14 and earlier, and in the editor that SmarterTrack uses in the latest version.
Andrew Barker
Software Developer
SmarterTools Inc.
www.smartertools.com