It's anybody's guess what Nintendo will be revealing in terms of surprises this year, although a new Legend of Zelda title would definitely hit the spot. However, there's one curious game that has seemingly already leaked. An image purportedly from Nintendo's booth at E3 indicates a new game called Mario Maker is in the works.
Although the shot from Nintendo Enthusiast is quite fuzzy, it does indicate that the game will let you tinker with the Mario formula however you see fit, through level creation and other goods. It shows a stylus, but both the 3DS and Wii U use a stylus, so that doesn't narrow down the platforms.
The picture appears to line up with Nintendo's general style of E3 booth presentation, but take this with a bucket or two of salt. It's a grainy, unsourced photo after all. If the so-called "Mario Maker" is legit, we'll probably hear about it at Nintendo's Digital Event on Tuesday morning.