In a recent Iwata Asks interview it was revealed that players will be able to use the Gamepad to capture a screenshot of the game they are playing. Players can then go to Miiverse where they can share these photos with others. Here are the full details from the recent Iwata Asks.
Kurisu: I want people to try Miiverse just by itself, and also try posting to Miiverse from games. If you spot a cool scene, you can post a screenshot by pressing the HOME Button. I truly hope people will actively participate in the communities tied to particular games.
Iwata: After you press the HOME Button, you can go from the HOME Button Menu to Miiverse. The game screen that was displayed at the time will be saved as a screenshot that you can post, right?
Kurisu: Yes. There’s a spoiler button, too. We’ve designed it so that people who don’t want to see spoilers won’t have to.
Iwata: There’s also a way to report something that you feel is a spoiler so it should be hidden.
Kurisu: Yeah. I hope people will make use of such features and enjoy aspects of Miiverse that connect to the games.
Source: Iwata Asks Interview