Using a casted shadow as a map

Hello, this is my first question on the forum, please address me to the right category if this is not the correct one.

I have a scene composed by 3 object, a hand, a spotlight and a surface. The hand is half meter over the surface, and the spotlight is casting the shadow of the hand over the surface. The surface is yellow and the shadow is black. I want to use the black shadow as a mask, in order to have an image inside the shadow, instead of the color black.

Is this possible?

search web !

here is one link

happy bl

Well, that thread was not really helpful, but this tutorial it was.

Instead of using the black color I can use any texture I want. Of course, this approach works good with planes, with other geometries, like for example a terrain, there are too many shadows