The character skins are replete with references and shout-outs to pop culture and historical or fictional figures.
MAX is one of only two returning characters; he was last seen proper in Bomberman Jetters.
And Star Bomber made his previous appearance in Touch! Bomberman Land 2.
Classic Bomber is a copy of his sprite from the original NES game.
Cyborg #0898 is an amusing one: he's a straight-up homage to the American boxart of Bomberman! The numeral in his name appears to be a reference to the release date of the TurboGrafx-16 in August 1989.
Bom Wayne is named after John Wayne, star of at least several dozen cowboy films.
Tutunkhabom's inspiration is Tutankhamun, the young pharaoh of Egypt.
Mahatma Bonji's namesake comes from Mahatma Gandhi, though his appearance is that of a stereotypical yogi.
Dragon Bom is a homage to legendary martial artist Bruce Lee, referencing his nickname, his "don't think, feel" quote, and even his iconic yellow jumpsuit from Game Of Death.
This is a strange one: Lady Bomjour herself isn't a reference besides representing French aristocracy, but her quote appears to be a bizarre mangling of the quote "let them eat cake," questionably attributed to Marie Antoinette.
Inspector Bolmes is named after famous fictional detective Sherlock Holmes.
d'Artagnan Bom is named after the character of the same name from The Three Musketeers (who was based off the guy with a much longer name).
Matryona Bomtryoshka is styled after a matryoshka doll.
Due to the nature of the game, it's possible whatever is unused will eventually see use in a future update.
This graphic is found among the items, its filename suggesting it's a "power-down" of the Power Glove, akin to the Bomb Down and Fire Down items. It's possible this appears in a stage I've yet to play, though!
The UI XML file (where all the text strings are stored) has strings for Mix It Up A Little stages 9 and 10, but no other data appears to exist for them.