Matte as replicator base shape?

I have some green screen footage and I would like the mask that it makes to be the image source for a replicator. What I have is a person and when masked it makes the person white and the green black. I want to take that white shape and 'fill' it with stars so I get the same shape, but with stars instead of a person.

I was looking at this tutorial (http://www.motionsmarts.com/tutorials/pain/pain1.html) as a start, but it uses a shape instead of a matte. Is there a way to convert a matte into a shape or something so I can achieve the desired effect?

Note that I do not want to replicate the matte, but rather use it as a base shape for a replicator to be used on.

P-Worm