Woah awesome! I love the tattoo! The only advice I would give is to add some shading and highlights, and adding some texture to the hair and maybe the clothing. For adding texture to hair, I like to put down the shadows, midtones and highlights for it first instead of going straight in with the hair strands, then afterwards use a fine pencil (hb-h5 or so) to add the strands of hair, thicker over shadows and thinner over highlights.
