Charcoal and Pencil: Mona Lisa

you probably heard of her before, right?
and why she smile? ( you been wondering what does it meant by hidden mistaken)
So first at all,
Original? No way! Leonardo Da Vinci created this masterpiece first! so all credit go to him..
and I try to redraw this one using only two material I pictured above!
My first error I make is having to do with arrangement. As I have a closer look, I started to notice that there is a problem with placing the wrong position of pencil ( which is on my artwork) 
So ,this artwork taught me three valuable lessons:
Never place anything on top of your artwork unless it is part of the artwork. 
Never leave too many space at the bottom.  
and finally, I should have gave my artwork a little neatness as possible 

Updated 7/28/2016: took a better photo and displacement of my art!