TSC Battle Artist Colour Study

Check your light sources, have two, moon and flame in your hand , try to imagine how it would reflect on the body , use of harsh shadows , always helps is using.
The use of textures is always difficult , in this case you used a fabric texture to the sky , I guess I wanted to simulate stars , I regret to inform you that out of tune too , it is more advisable for a small brush.
Play more with colors , an example would be the mountains are green one , try to use different shades that will make it look more neat.
And finally do not know what program you use to paint but imagine having layer mode , so my advice would be playing with layer modes, for example for lighting effects are very useful .
I particularly use 4 layers
1.Lineart (normal mode if the lineart is transparent or multiply if it is not)
2.Luces (normal mode with 30 % opacity , always use white brush )
3.Sombras ( multiply mode variable opacity between 30 % -80 % , always black brush)
4. -Flats (normal mode)

When I finish with that, then I get to play with the layer modes and change colors, double coats , etc. experiment ... that's my advice

Sorry for the bad English , I use google traslate