A great piece, that really sends your mind in aww from the blend of dark tones and shades. The light tints really stand out, but the main thing about this piece, is the blood effect. It really stands out among all of the eery colours, making this truly an eye catching piece of art. The slimy grayish green colours, make it distinct that he's in a sewer. I like that about a piece of art, being able to tell where the picture is set, saving you time on pondering about the place rather than this excellent piece of art work.
i use box shaped brush to make the first rough idea of the pose and background, and hard round brush for detail parts, yes i make the box shaped brush by myself because there's no box shaped brush in the original photoshop brush set. i hope you understand ^^
i use square brush at the beginning just to make a silhouette of the object i'm trying to emphasize ^^ well, if you want more cleaner artwork you should start with a hard round brush all the way to the end, but if you want to give it abstract feeling then you should start with square shaped brush, because square have "edge"? i hope that make sense to you ^^