So I thought about a 3DS-style Wii-U OS and this is what I came up with (last mock-up for today, don't fear!):
The basic idea is that you select your channel on the controller. Notice the two dots on the bottom? Yeah, they mean than there are currently two homescreens and that the first is selected (just like on iOS).
If you choose a channel with the stick or with your finger, it will get a blue frame and the logo of the game will show up on the screen. You get information about how many coins you collected, when you've played the last time and if any friends are playing this.
In this case, there are friends who are playing this. If you press the NIN-logo on your controller, it should directly link you to a list of friends who are playing the selected game. Otherwise this button opens up the NIN menu with more options, friendslist, chats, video chat, and so on.
Hope you like it, GAF!