This is seriously really cool. I love the shading in the hair and you're seriously killing it with the attention to detail on the tattoo, I would not have the patience for that! XD
However, shouldn't this be tagged NSFW on account of the nudity?
But man, that is some seriously nice effects you have going on in the background. I have no idea how you did any of that with watercolor, I can't use water paints to save my life lol.