I've always been a bit confused about them. We know they have official artwork but there's little else on them.
From what I've heard it seems like they were put into an early version of the game, sprites and all. It seems a bit unusual for Game Freak to get this far along with the starters only to completely change them later on. But what startles me the most is the fact that if this is true, we have no video footage or screenshots of them. Nothing at all other than their artwork.
Is there a proto-GS lying around somewhere with them in it?