it's fine as it is. In fact I think it would have ruined the whole feel and aspect of the image if you would have gone into detailing and working more on it.
It is a verry sylyzed picture. You could see this as a styled flattened image of an octupus, that got re-detailed and stuff like that. So yea, i know what you mean, it has no perspective, but on the other hand, it was never meant to have any perspective.