I doubt that this is documented. You can take a look at how the My Computer
icon is placed there and try to do something similar. My feeling is that
you're likely to spend a lot of time for nothing and will end up with just a
shortcut, maybe marked as read-only, in the \windows\desktop folder anyway.
If having this desktop icon and preventing the poor user from getting rid of
it is a very high priority, start browsing the registry on the device with
Remote Registry Editor. If you can't find anything that will work, expect
to rewrite at least part of the shell to prevent deletion of your shortcut.
Paul T.