how to add system icon for all users

Hi,
Let me preface this with I'm a graphics guy, not a technical one so forgive
me if I sound like an idiot. I've created 4 new icons (.ico files) for our
small department to use as folder icons on our department shared drive.
Another person in the dept has the icon files saved to her desktop too, and
we can each change the folder icons on our respective computers, but the
folders I create in the shared drive show up on her computer with the default
Windows folder icon just as folders she creates appear with the default icon
on my screen.

If I change a folder icon to one of Windows other standard icons, all of us
see it the same way, so my guess is our new icons need to be saved somewhere
else, perhaps on the server?

QUESTION: Is it possible to save new .ico files so that when I make a folder
using one of the new icons on our shared drive, everyone who has access to
that drive sees the new icon as well? We use Windows Vista.

Thanks!