Zhangx, I've been following you for a while and I only have one thing to say: YOUR ARTWORKS ARE AWESOME! I'm a big fan of everything that relates to science-fiction you see, and finding your artworks has been like stepping on a goldmine for me. And for giving me that kind of happiness, I thank you deeply.
But say, how exactly do you draw your pictures? I mean, when I zoom in on this picture, I see that you haven't put in the black "lines"(?) that normally separate different elements on a picture, but rather that you've used different colors and tonalities to separate and define the different elements of the picture.
Oh, I forgot to add, I hope that saying cel-shade will help with understanding what I meant with the "lines". I don't really know a lot of art vocabulary, so cel-shade probably isn't the most appropriate word.