UE3 - UT3 Import texture in light (is that possible)

Hi
I need some help.
My plan is to cast a light (using Spotlight) onto a wall.
The light on the wall should have some kind of texture image, as if the light shines through an object.

example: on the wall one can see the light with a shadow that looks like branches of a tree.

So my question is:
Is it possible to import somekind of image onto the light-settings to create that kind of effect.

Thanks in advance.

thx for the help, but have a new problem now with the light functions.
It works fine if I have multiple textures, but when I want to use the "Non tillable" as descript on book.hourences.com
first of all when I only add the "Panner" and input the coordinates, the texture will flicker and change position all the time. When I then add the Constant in the material editor, the material turns white.
Any ideas why that is happening?