Thanks for the answer. I ended up stopping using 3 Luna_Q Plugins because it was causing too many problems. Instead, I just use GALV LayerGraphicsMZ.
Your plugin works great on the normal map, but it still doesn't show the shadow when I use the layer (just an image as layer). I think it might be because this image is on a higher layer than your shadow system is using, so it is overlaid. Can this be fixed? Thanks a lot.