Gswitch automatically changes your GNOME desktop background every so often. The backgrounds are displayed randomly. All background images and style settings are sourced from your list of backgrounds as configured in "System > Preferences > Appearance". By default, images are switched after 20 minutes. Although the images are shown randomly, every image will be shown at least once before you see any repeats.
Compa is a GNOME panel applet which can display the output of any system command on the panel. It can also display the output of a different command in its tooltip, and launch a different command when clicked. The text style can be modified using the Text Attribute Markup Language.