You need to work on how light is captured when it hits something or enters an area. You also need to work more on detailed shading. The girl in the front's butt looks severly flat, no curve at all; her back is a solid board. If you were to glance at it, you could see what is wrong, though you may not know why. You have a good style, but I can see that you can do better (her hand is proof). Just take some more time with it. Don't do more detail in some areas and not others. But keep enough detail so that objects can be seen correctly. The more detail the better, but don't need to go crazy with it; moderate. But the less is easier; compliment the drawing with the coloring with the everything else. Also, I like the idea of doing something see through, but you need to work on what rules you are using for see through; how much will allow, how much would disallow, how see through is it, how close or far must it be to be see through, how does it light when see through or not, how do these levels blend together. You have done better in different aspects with some of your other work, just need to put them all together.