Well there's a point to be made with this, i dont believe any of us have a demon fox seal within ourselves, so we can't all be sure.

IMO i think Naruto could have more of a mental image of kyubi, something more of a feeling towards him, since you would probably have something like that inside of yourself, after awhile of knowing it, and from past expriences when he tapped into kyubi's chakra, he could probably get a feeling of what he may look like.

idunno just me i guess.