Hobbes said:
The romanization, it would be interest to compare it to the Foreign Names table of each item/character/whatever.
Ok, here are the various romanized names (they are all in uppercase). The format is card: "English name (not on the card)" - "Romanized name on the card"
K♠: "MARIO" - "MARIO"
Q♠: "PEACH" - "PEACH"
J♠: "LUIGI" - "LUIGI"
10♠: "WHOMP" - "BATTAN"
9♠: "LEMMY KOOPA" - "LEMMY"
8♠: "KAMEK" - "KAMECK"
7♠: "BOB-OMB" - "BOMB-HEI"
6♠: "KOOPA TROOPA" - "NOKO NOKO"
5♠: "BOO" - "TERESA"
4♠: "PIRANHA PLANT" - "PACKUN FLOWER"
3♠: "WARIO" - "WARIO"
2♠: "BABY MARIO" - "BABY MARIO"
1♠: "SUPER MUSHROOM" - "SUPER KINOKO"
K♦: "CAT MARIO" - "NEKO MARIO"
Q♦: "TOADETTE" - "KINOPICO"
J♦: "TOAD" - "KINOPIO"
10♦: "PETEY PIRANHA" - "BOSS PACKUN"
9♦: "IGGY KOOPA" - "IGGY"
8♦: "MORTON KOOPA JR." - "MORTON"
7♦: "SPINY" - "TOGEZO"
6♦: "GOOMBA" - "KURIBO"
5♦: "SHY GUY" - "HEY-HO" (actually the artwork used is that of a Fly Guy)
4♦: "CHAIN CHOMP" - "WANWAN"
3♦: "WALUIGI" - "WALUIGI"
2♦: "BABY DAISY" - "BABY DAISY"
1♦: "SUPER STAR" - "SUPER STAR"
K♥: "FIRE MARIO" - "FIRE MARIO"
Q♥: "DAISY" - "DAISY"
J♥: "DONKEY KONG" - "DONKEY KONG"
10♥: "WIGGLER" - "HANA-CHAN"
9♥: "ROY KOOPA" - "ROY"
8♥: "WENDY O. KOOPA" - "WENDY"
7♥: "CHEEP CHEEP" - "PUKU PUKU"
6♥: "KOOPA PARATROOPA" - "PATA PATA"
5♥: "LAKITU" - "JUGEMU"
4♥: "BULLET BILL" - "KILLER"
3♥: "DIDDY KONG" - "DIDDY KONG"
2♥: "BABY PEACH" - "BABY PEACH"
1♥: "FIRE FLOWER" - "FIRE FLOWER"
K♣: "TANOOKI MARIO" - "TANUKI MARIO"
Q♣: "ROSALINA" - "ROSETTA"
J♣: "YOSHI" - "YOSHI"
10♣: "DRY BOWSER" - "HONE KOOPA"
9♣: "LUDWIG VON KOOPA" - "LUDWIG"
8♣: "LARRY KOOPA" - "LARRY"
7♣: "BUZZY BEETLE" - "MET"
6♣: "HAMMER BRO" - "HAMMER BROS."
5♣: "BLOOPER" - "GESSO"
4♣: "BIRDO" - "CATHERINE"
3♣: "LUMA" - "CHIKO"
2♣: "BABY LUIGI" - "BABY LUIGI"
1♣: "? BLOCK" - "HATENA BLOCK"
JOKER: "BOWSER KOOPA" - "KOOPA"
JOKER: "BOWSER KOOPA Jr." - "KOOPA Jr."
The deck is actually organized according to some rules: K is Mario or one of his most famous transformations, Q is a "princess" (and Toadette has already been associated with princesses, as in the Mario Hanafuda deck she is with them: https://www.nintendo.co.jp/n09/mariohanafuda/index.html), J is an important playable character, 9 and 8 are Koopalings (but in the case of ♠ we have Kamek as the Koopalings are only seven), 2 is a baby and 1 (not indicated as A) is an item. Even in the other decks Bowser is in the Joker cards, so it made sense to have Bowser and Bowser Jr. as Jokers.
Regarding the romanizations, I think the interesting part is Kameck, Kinopico and Packun Flower, usually romanized as Kamek, Kinopiko and Pakkun Flower, also the Bomb-Hei, Hey-Ho and Hana-Chan names now have a bar (Hey-Ho also uses the y, while Bomb-Hei finally has the missing b!). Lakitu is Jugemu again, too.