If you can find a way to do it without too much hassle, I suggest putting a transparent panel in the base as well. It’s often really useful to be able to have light shining downwards.
I agree with Jim about painting (or removing) the scorched wood.
I’m not sure about the weathering… it depends on whether you want it to be new or old IC. Equally, you can make it fancy or utilitarian, depending on your character’s personality, nation etc.
Having Diras on a light source seems a bit strange… but now I’m imagining the Diras panel having its inside surface treated with a black paint undercoat (or black paper) and then a white or reflective topcoat, except where the rune is, so that from outside the panel lets no light through except the rune itself which would be glowing against a black background.