An update to the popular custom launcher ADW EX was released today, and it adds a feature many ADW users have been clamoring for: custom dock backgrounds. While it may sound trivial, some have used the lack of a custom dock option in ADW to declare Launcher Pro the superior app. ADW EX comes with 8 of its own custom docks, though you can use any image from your gallery as a dock background. The update also includes a few additional customization options (you can find the full changelog here).
To get the custom docks, hit the Menu button while on a homescreen, select More, ADWSettings, UI Settings, Main Dock, Dock Background, Custom.