JRieke, I like the way you think! The trick will be stopping the image (light in this case) from passing through the glass. You might try some slightly opaque mylar type material.
Who knows, you may create a new "Hybrid" analog/digital impressionist fad.
I tried using my G9 as a slide scanner last fall. I put the slides on my light table and set the camera to macro. The results were less than stellar (huge pin-cushion effect), but I managed to entertain myself for a while.