A picture of the alleged Nintendo E3 booth has been circulating the web for the last 24 hours, showing what could potentially be a new game, Mario Maker. It looks to be a custom stage builder and editor for Super Mario Bros., making use of the stylus to add and remove blocks and enemies.
If Mario Maker proves to be real, it is likely there will be a strong social aspect, including sharing levels with friends and setting challenges. Whether Mario Maker will be a small-scale, standalone game or a stage building section of another game is yet unknown, so we do not know if there will be any cross-game functionality, such as being playable on the new Smash Bros.
Both the Wii U and the 3DS use a stylus, so it is still unclear which console Mario Maker will be released on, or if it will be a cross platform release. Until more information is released other than the rumours surrounding this low resolution image, we can only speculate.
Source: Nintendo Enthusiast