We are currently working on the documentation of RadImageEditor. You can check this blog post for starters. In addition, the code of the online demo can be seen by switching to the Source tab in the top-right corner of the widow. The example is also included in the zips which are available for download from your account.
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!