The Main Index will, by default, show the logos of Beavers, Cubs and Scouts (and optionally Explorers and/or Network, or none at all). They are styled to line up with the Boxes (so they may look out of bonk above) and they are linked using the URLs configured in the theme. The Logos are implemented as a separate module that can be loaded in to any page template as many times as you like but they are styled to work on the Main Index so they might not look quite right on other pages without additional work.
The Explorers logo may also be displayed. The logos are styled to be roughly evenly spaced rather than aligned to any grid.