Light can penetrate skin, but not enough to project much of an image without frying you.

So get the strongest light source you can find and fit in your mouth and try to project through your cheek. I've never seen more than a dull glow from doing this, but maybe you can draw on your cheek with something super-opaque and project an image. I doubt it, but it probably won't hurt you to try. Stop if you feel an intense burning sensation.