I love "Carnival"... so much that I don't want anyone else to do a cover of it. I always sing the harmony part when I play the song!
I can imagine SR singing "Carnival" though... but it would feel totally wrong. Frankly speaking, I don't quite like any of the Cardigans stuff after First band on the moon. Maybe "I need some fine wine and you need to be nicer", I think SR can do that song.