I wouldn't call the Opera browser a new Channel for the month because its 3rd party, and not Nintendo, plus you have to pay for it.
A new channel that is based around the Miis would be good, a virtual world - but N isn't going there, unfortunately because I think it would be pretty good to interact with others in that way. A chat channel, unless via microphone would be hard going - imagine trying to chat using the virtal keyboard. Too slow.
The Mii vote channel sounds lame, IMO.
A demo channel would be great, but unless you've got a large SD card, its not going to work too well. You need large temporary storage space.