Well that's why what they did with Navi is so clever. It doesn't contradict the concept art. She's just so bright that her body is completely obscured by the light, but it's still in there. It also ended up looking much better than what they would have gone with if N64 had been more powerful. Really it makes sense since Tinkerbell has long been portrayed in stage plays by a light being shined upon the stage.I have a saying I like to use:
"What I see in the game is canon" and I mean it literally. Concept art looks cool but the way everything looked in Ocarina of Time is what it was, on face value. That's why I love how in Metal Gear Solid 4 they didn't try to re-render the events of the previous games in the flashbacks, they simply showed them as they were, because that is the truth.