The Lightning Chariot Tower, the Lunar Sanctum, the Thunder Cloud Temple, the Aurum Fleet, the Chaos Vortex, the Space-Pirate Ship and the Underworld would all make interesting Kid Icarus stages. That isn't surprising, considering Kid Icarus: Uprising boasts some of the best graphics on the 3DS.
With Arena Ferox, Reset Bomb Forest and Rainbow Road revealed for the 3DS version, I wonder what will be the stages for Fire Emblem, Kid Icarus and Mario Kart on the Wii U version. Maybe there will be two Fire Emblem and Kid Icarus stages per version? It's a bit of a stretch, but I would like it. (Or at least, bring back Castle Siege and Skyworld.)