i believe that the characters on the sides of everyone's profiles(except kanon, i think??) are meant to be their closest friends, or the people they trust the most!! i'm not 100% sure if this is true or not, but it seems to be the most likely answer,,,
as for the flowers, i believe that everyone's flower seems to be associated with a flower meaning- i even looked them up myself!! a majority of them seem to be pretty accurate!! some of them don't make a ton of sense(lyle's in particular, though it may relate to his friend...), though that could just be because we looked at different sources :')
please be aware that i'm not well-versed in flower meanings(though i'm interested in learning about them), so some of these might be incorrect!! feel free to correct me :)
art - bouvardia: enthusiasm, versatility, the joy of life, celebrating life, happiness, and light-heartedness
pandora - daisy: new beginnings, rebirth, love, cheerfulness, beauty, purity, innocence, hope, fun, and affection
sei - purple hyacinth: sorrow, "i am sorry." a deep feeling of sadness and asking for forgiveness
kanon - marigold: power, strength, and light that lives inside of a person. also can represent positive emotions and energy, though this doesn't seem to match with kanon's character
echo - gladiolus: strength of character, remembrance, faithfulness, and moral integrity
forte - calla lily: the idea of life and fertility, and on the flipside, it's a well-known symbol of death. this might correlate to the comedy and tragedy masks, also being positive and negative opposites, linked by forte's theatrical ultimate
cyrus - snapdragon: deception (perhaps tied to the notion of concealment) strength, and graciousness. they were historically used as charms against falsehood
lyle - asphodelus: mourning, the underworld, death, peace after death. seems a bit ironic, considering... as said, it could be related to "his friend," who i'll keep secret for now for spoiler purposes. i'll talk about it in a separate message, if requested to
on other topics, aspholdelus is quite obviously linked to the underworld, so much as to be named similarly or after the greek middle afterlife: asphodel. it was made for people that weren't particularly good or bad- average people
missy - geranium: clever minds, ingenuity. as well as happiness, good health, good wishes, and friendship. the first two seem to fit missy best
ashley - white carnation: purity, sweetness, simplicity and genuineness. as well as "expressions of pure, wholesome love"
some of these flowers(the asphodelus, more specifically), don't have a lot on them, flower meaning-wise, from what i could find, so they might have additional meanings that i missed. let me know if you find any significant ones!!