Hey man! Cool stuff you got there. There are many things going on, but overall, design is not necessarily what is lacking the most.
I'll start with design though. It looks like you're going for a technological style, and I do appreciate the way you've divided things into panels or shapes. Like a car, its made of several pieces. A lot of your design is unorthodox, its different. I think you would greatly benefit to look at some modern sci-fi outfits or characters, and just observe their design. Maybe try to replicate your favourite characters, and figure out the shapes.
It seems that you have a balance between too many details and no details, making it pleasant for the eye to look at.
I think mainly, your shapes are off. Your creatures/characters feel squished and without structure, and working with perspective and shapes will help you quite a lot. I think you'll need to take some time and learn anatomy as well, as there is a lot to gather from there. Besides that, your values are a bit chaotic, always remember that you can use values to guide the viewers eyes. Your values aren't very realistic or cartoony. If you were going for realistic, you need to do some more studies to figure out form and values! 
Either way, good job with them! hope this was helpful!
