Love the art, but I've got to say: the perspective on that floor makes it look like that one scene in Inception where the floor rises up to turn into a wall.
Always had a knack for perspective, so it's kinda hard to teach other what it is. Best advice I can give is
>practice drawing backgrounds by using photos as references (liminal spaces have got you covered there)
>drawing cityscapes (those are basically just a bunch of large cubes with windows)
>using something like a square mat under your feet when you're taking body references in order to get an idea of where the perspective is on your character (can get tricky depending on the type of lens you're using since some tend to warp the image a bit more than others)
>And I've heard people using Minecraft to construct their environments. Since it's so easy to build things in Minecraft and the cubes makes perspectives easier to find.
Hope that wasn't too much of a mouthful. Always love seeing people improve at the things they like