They aren't bad for your first few. The first thing I notice is lack of a color theme meaning that your colors seem to just be randomly chosen. It's hard to go into detail about how to fix the colors and stuff because each one has it's different problems but in a general sense just try and match your background colors and effect colors to the render.
I'm kind of getting tired so I'm going to stop there but try and work on your color schemes and post some more and I'll see what you can work on next.