If you're gonna have black in between the letters, then it clashes with the red background, so you would need a backing of some type.
Either that, or remove the black and have it transparent.
I don't use Photoshop, I use Paint Shop Pro so I'm not much help with Photoshop even though I know how to use it if I really REALLY need to.
I see you've got more similar art styles now because of the Harmony of Despair characters. Right now the only clash I see is Olrox. Stylized Soma looks pretty cool... but you cut out the right side of his head.
You're going to need a backing or an effect behind the character collage. Some parts (like where Hammer is) look fine, while other parts (behind Charlotte's cape and behind Arikado's hair) there's some White. You need consistency so you should consider either adding glowing edges to the entire collage, or a black border. I realize Charlotte's cape has white on the edges but it doesn't look good against the background.
Just some opinion.