The Decorator class' sole purpose is to provide visual markers or meant purely for ornamentation. Icons and target reticles are among the most commonly used decorators in a user interface. The GLAM toolkit provides both PNG and SVG icons. Of particular worth are SVG icons, which can be indefinitely scaled to any size.
The most important aspect to decorators are their visual representation. To modify a decorators visual representation, a developer can sub-class the component and overload the various render methods.