Millie is correct; Decker doesn't attempt to manipulate native image data in the system clipboard; it's very difficult to do that sort of thing in a cross-platform fashion, especially once web browsers are added to the mix.
Decker uses a custom text encoding for information stored in the clipboard. If you're interested, it's described in The Decker Document Format. This is also the same format for images you can obtain with the ".encoded" attribute of image interfaces.
Keep in mind that anything you find yourself doing repeatedly in the Listener can be moved to a button script, and parameterized with other widgets. Use Decker to build tools to remove tedium from working on your projects!
