Because it comes directly from Nintendo's retail training site, we can assume Nintendo sees this box art as acceptable to use on an official level, at least until the final box art is designed. We've seen this artwork before in magazines (EGM, to be specific) and it's unlikely that Nintendo would use this as their final product. However, we do see the Wii logo at the top and this might be a good indicator of what Wii games will come looking like.

Source