I ran across these pictures and I thought they looked interesting. And when I mean interesting, I mean legit. =)
If you follow the link below, you'll see two sets of pictures. One set is grainy... obviously not directly lifted from a game. The second is a bunch of crisp Mario-style hills.
The first (grainy) set is the only one that looks real to me. It looks as if someone took some pictures during a Nintendo presentation. The screenshots look very much along the style of Mario Sunshine, but of some areas that I've never seen before and with a slight difference in the interface (a star or flower in a pocket at the bottom right hand of the screen). They don't reveal a whole lot, except that we see Luigi, but it's still interesting. Unless it's an area that I haven't seen of something that has already been released, I would believe these were real.
I really doubt the second ones are real, though. They don't really seem to be in the Nintendo style. The colors are a bit off and the hills look plastic-y. They'd be pretty easy to fake for anyone with some 3-D modelling software.
Total Video Games- Mario 128 Screenshots?