I really enjoing your style! Some pictures looks outstanding and pretty funny!
I'm not best critic at all, but here is some deals:

1) You need to start to attend to details. Some your works look empty and even borring sometimes.

2) Try to use references, like photo of landscapes, human or animal anathomy and etc. Even THESE kind of pictures works well.

3) Color paletters are very usefull! Try use them too! Here some links which helps you a lot:
https://kuler.adobe.com/explore/most-popular/?time=all
http://chromaa.tumblr.com/

Also, I've got a question: do you use tablet when drawing?