There are many reasons why you might be interested in purchasing a lightbox. For some artists, they are indispensible. A huge part of the tattooists work, they are needed to trace designs and work out ideas.
Charcoal is a great medium to draw with, and if you never have then I suggest you give it a try. Not only can you get the best shades, but you can go into further depths with the charcoal than with any other type of medium that is out there.