Hi Christian
Have you looked at the Sun online book
Java Look and Feel Design Guidelines? A lot of this book revolves around designing individual components, but it also goes into windows, panels and the like. From the "who should use this book" section:
Although an application's human interface designer and software developer might well be the same person, the two jobs involve different tasks and require different skills and tools. Primarily, this book addresses the designer who chooses the interface elements, lays them out in a set of components, and designs the user interaction model for an application. (Unless specified otherwise, this book uses "application" to refer to both applets and applications.) This book should also prove useful for developers, technical writers, graphic artists, production and marketing specialists, and testers who participate in the creation of Java applications and applets.
Java Look and Feel Design Guidelines focuses on design issues and human-computer interaction in the context of the Java look and feel. It also attempts to provide a common vocabulary for designers, developers, and other professionals. If you require more information about technical aspects of the Java Foundation Classes (JFC), visit the JFC and Swing Connection web sites at http://java.sun.com/products/jfc and http://java.sun.com/products/jfc/tsc.
The guidelines provided in this book are appropriate for GUI applications and applets that run on personal computers and network computers. They do not address the needs of software that runs on consumer electronic devices.
Regards, Andrew