Yeah, that's not what was up the other day.
This new one is just the "placeholder" image they look to have for all of their DS preorders. Just the logo from an old game in the series (their "Mario Kart DS" one even says "Super Circuit"), with a DS logo stuck on the top, and an "RP" ratings logo photoshopped into the corner.
Yesterday thay had a much better image (although still not exactly an awesome one) with an actual "Super Mario 64
DS" logo on it (which isn't exactly a term that's been used for this game before now), and Mario, Luigi, Wario and Yoshi (?) all standing in a pose, ready for battle, as if they thought they were on the cover of a Mario Party game or something (the exact pose looked new to me). There was no cheap "DS" logo tacked onto the top, but it had that white GBA-style curve on the side of the box, which is (or rather, used to be?) visible in that SpiderMan box art thread.
But, for some reason, GameStop pulled the image that they had, and replaced it with this generic "Super Mario 64" placeholder.
Edit: Forgot the spooky emoticons.
Edit#2:
Here's the boxart that was on GameStop, for anyone who missed it.