That is a LOT of characters! Are you going for a sort of Homestuck thing where the narrative keeps shifting viewpoint? It'll be really hard to manage a cast of that size.
I spent several minutes looking at these, trying to work out why I was getting the impression of "sameness" when there aren't elements that are the same across all the characters. I think the issue isn't necessarily that the characters all look the same, but that there are a few pairs or trios of characters who if you were to describe their appearance, they're really similar, like "The pale, dark-haired one with lots of silver piercings" or "the gothy one" could refer to four characters out of this lineup.
Other characters are immediately easier to categorise and remember, like I'd find it easy to remember "cat boy", "princess", "6 eyes", "red hair" etc. They're all very visually distinct and when I look at them I immediately feel like they stand out from the rest of the cast.
There's nothing wrong with any of the gothy characters' designs on their own, they just maybe look a bit too similar to each other, especially Belora, Nerara and Menyne, who all have this sort of similar look. Maybe consider how they differ from each other in personality and interests, like maybe one of them could be more pastel goth with pale hair for a more ethereal look, and maybe one wears black, rather than silver piercings and has gauges and wilder, more spiky hair for a harder, more punk edge, as examples. I'd call those three the main problem area to look at.
