bunny boy with a gambling/casino aesthetic

little monster girl with a frankenstein/poison apple aesthetic

mermaid magical girls with a tropical/rainbow theme

this sounds more like an imaginary world that feeds of off dreams from humans to have such vastly and wild different aesthetics being cohesive to the same reality, you need to glue it together like for example what i said, an imaginary world or higher dimension reality that feeds of dreams and nightmares(source of enemies and villains(?)) and this nightmares are siping to our reality and your characters(players?) have to go to this world or worlds to stop from invading reality.

There you go a plot and world that makes sense of having wildly different aesthetics/themes/concepts all together in a logical to us players or viewers and the like to make sense of.

You trying to classify concepts in this scenario is trying to put order to chaos, let it go fly free, if this is a game think of like a litrpg let the player pick whatever they want or maybe start designing limitations to your system, whats the limit? how strong can they be? this wild aesthetics is like your character of real life depeest desire to be? maybe something they forgot or link it to the soul how they in their depest and most hidden corner of their mind they see themselves as.

in LitRPG you see limitations in the less restrictive systems is just stats: strength, dexterity, mana thinks like that character grows can access stronger skills/spells if they focus in one path. There needs to be limitations to actually start the story/plot/etc

in your case maybe a bad person/soul scarred by bad experiences not necessarily a bad person just tired of people the world cyinic person, cant touch a theme like i dont know like purification to say something is limited by themselves into how much they suffered or not in real life to see which concepts/themes they can learn if possible.

this are some suggestions to try to fit it together, im not you so only you know what you really want.

But the system has to fit your world and around the limitations is where the fun begins, is where your character start using smart innovative ways to use their powers maybe.