Ok guys, this is not the printed one. I just going crazy when I saw this cover made by Eddy Barrows [link]
with all those shapes of gray made in pencil. Here is the original, take a look: [link]
Then when he sent me, I tryed a classic painting style, something using a kind of flamengo painting, what makes the background appears, fast brush strokes, etc.
Hope you like it, this is one of my favorite works!