UI sketch:

Demo Suite
  Modules
    Demo Module #1
    Demo Module #2
  Branding
    Resource Overrides
      Core
        org.netbeans.core.resources
          splash.gif
      Core - Windows
        org.netbeans.core.windows.resources
          frame.gif

*Resource Overrides* contains subnodes for each platform module which is to be
branded, named according to the display name of that module (or code name base
as a fallback). Each subnode contains a package tree of branding resources which
are to be packaged into the application. For example, if the branding token for
this app is set to be myapp, the above diagram shows that when built, the
application's cluster will contain (among other things) a file
modules/locale/org-netbeans-core-windows_myapp.jar with an entry
org/netbeans/core/windows/resources/frame_myapp.gif, which would have the effect
of overriding the icon used for the main window (if
modules/org-netbeans-core-windows.jar!/org/netbeans/core/windows/resources/frame.gif
normally specified it - just for example).

The developer can directly edit these resource overrides or even create new ones
using the usual file manipulation idioms, but the normal workflow would be to
use wizards and other controls to override branding items. There is no GUI to
add a particular module to brand (other than through the higher-level tools),
but all of this file tree simply corresponds to files in the suite project. For
example, frame.gif in the above example would be located beneath the suite
project's folder with the path
branding/modules/org-netbeans-core-windows.jar/org/netbeans/core/windows/resources/frame.gif.
The suite build process will automatically package all files it finds beneath
branding/ in the appropriately named JARs.

Context menu items:

   Override Icons...

Would open some kind of wizard or nonmodal dialog letting the developer browse
icons present in the platform and override selected icons with their own choices.