Linux only: Similar to Mac OS X application Geek Tool, DevilsPie is an open-source application that allows you to control how specific elements of a window appear. The Ubuntu Forums explain how DevilsPie can be used to embed a Gnome Terminal session into the desktop.
The objective is to have a gnome terminal running as the desktop background, right above the actual background image, that won't be displayed by the statusbar or ticker.
The process requires installing DevilsPie, creating a configuration file, customizing a Gnome Terminal session, and adding DevilsPie and the Gnome Terminal to your list of startup programs. Although this process is outlined in the Ubuntu Forums, it should be extensible to any flavor of Linux running Gnome.