Whilst you invent them and control them, that control should not be to the extent they lose any sense of personality. You don’t want puppets. Leave them to Thunderbirds ….
Think about flora and fauna.
Even sci-fi/fantasy worlds have their ecosystems, predators and prey and so on. And especially in a fantasy world have a look at how magic affects them. For example does it make them more aggressive? Do they need magic to live at all? Could they survive on earth? Would earth be beneficial or harmful with no magic about?
Does your world have specialists?
Eileen is a specialist in her field, as was Rose. Does that lead to envy in others or are the specialists left to it as they face more risks than most?
What threatens your world?
Has it done anything to deserve it?
How do your characters’ lives change?
Long term characters especially should have plenty of ups and downs. The ups shouldn’t be saccharine sweet. For the downs, there should be some hope they can get out of them. (If you want constant despair, watch your average party political broadcast!).
Do your characters develop relationships?
Think about all kinds of relationships as well as the obvious romantic/sexual ones. Is there part of their personality that makes forming relationships difficult? Do they find a particular type of character difficult and if so have you shown why?
How do your characters’ relationships change?
Relationships don’t stay static. Relationships should be a major part of your plot, should complicate things and give your characters both hope and despair. Think about how your character demonstates anger, frustration etc.