I don't like this. And before you brush me off for just being some asshole on the internet, here is why:
It's because I look at this and I don't see Marceline. Marceline isn't 'cute'. Marceline isn't meek, quiet, bashful, or withdrawn, which everything in this picture implies. Her pose, her face, nothing about it is right. She is also too green, rather than grey. It is terrible fan art. Sure, it's artistically sound, but it's terrible fan-art, because - to me - this isn't a drawing of Marceline: The Vampire Queen.
Yeah, I see where you're coming from.. and you have a right to dislike something, I respect that~ I guess I just let too much of my style rub off on her, and had too much fun dressing her up in clothes that weren't from the show xd