That is so awesome it's scary! :o :o I love the Mando skull. Perhaps you could dremel it out and then place an accent LED behind it to light it up? ;) ;)The skull and the stripes are dremeled it is just so tight to the main body I don't know how to go about placing the leds. I thought about using a film behind the skull and light it bottom up. I don't know.
One way to do it would be to cut away a window behind the skull, and replace the wall with a semi-tranluscent material (a slice from a round shampoo bottle works nice). Then, wire in an accent LED or two behind it to illuminate the skull cutouts. When the saber is off, the material will block people from seeing into the battery back.
There is a brand of shampoo out there that uses a dark orange-ish bottle that is semi-transparent. A 5mm white LED shining behind this material would match your Amber LED the closest, off the top of my head. Try to stay away from films, since they are flimsy and can crinkle. The semi-trans plastic stuff is a good bet because not only is it flexible (so it stays in place easier), but these days you can find bottles molded in a variety of colors and levels of transparency, and they are also relatively strong.
Good luck with it. Even without the illuminated skull it is still a very impression saber.