You can "leave out" any file that has an icon on the desktop. For example, you can go into your Workbench:System drawer, click once on the "Shell" icon to select it, let go and then hold the right mouse button to get the menu up. In the "Icons" menu, you should be able to see a "Leave Out" option. If you choose that, it will leave your Shell icon on the Workbench screen. In reality, nothing is actually moved (workbench keeps a file in the root of each disk partition called .backdrop that contains a list of left out files).
If you want to put the icon away again, you can just select it again and choose "Put Away" from the "Icons" menu.
You can do this for any file that has an icon.
