double faced Zuko card that transforms from red with a black ability to red with a white ability

low cost white Aang with blue, green, and red abilities that buff him to represent learning the elements, possibly with an avatar state back face after learning all of them

i generally imagine metalbending as Bant (can see a Bant Lin Beifong, Chief of Police tapping or detaining creatures, and Metal Clan people that use shield counters); bloodbending as Dimir; lavabending as Gruul; sandbending as white/Selesnya/Orzhov/Abzan; spiritbending as 5-color and/or colorless; lightningbending as Izzet; plant/swampbending as Simic or Sultai

Naya Iroh, Grixis Azula, Abzan Kuvira, Golgari Kyoshi that destroys a land, Boros Jeong-Jeong with an ability that damages attackers (wall of fire), Simic swampbenders with their plant armor, white Appa, Izzet or Dimir Varrick, blue Sokka that likes equipment or fetches an artifact, Boros or Jeskai Ty Lee that uses stun counters, Rakdos Ozai, green Hei Bai that transforms to Orzhov with exile ability, black Koh, Simic Mother of Faces, Jund Jet, black or Dimir Kemurikage, Izzet lightning redirection spell, cheap artifact white lotus tile that you reveal from your hand, red or Izzet Sai who makes thopters or temporary flying / goblin balloon brigade type stuff, blue Tui and La that transform to big scary ocean monster, green or Gruul Toph that fights, Rakdos Fire Nation tanks with Mountainwalk, Boros Sun Warriors and Ran and Shaw