This is a wonderful job. You’ve neatly captured a style and applied it to both hard surface and organic shapes, making them unite in the same world. No easy task! You certainly have a good eye for design. The only advice I could offer is to vary your hoodie just a little, or change the background color a bit; she bleeds right into it. I realize your focus is the hardsurface helmet thing, and it stands out beautifully in the upper shots, but so does her skin and face. Perhaps if you make it a shade of green, or a more saturated blue? Even an additional rimlight would do the trick. I did notice you have a touch of red light stage left. Perhaps just making this stronger would work. Darkening the background in the ones with just the helmet would make it a little easier to see the lighter pieces, as well.