I thought i would give my two cents in this thread before i went to bed. I'm confused on why there are so little posts in this thread, there are always 30+ people looking when i visit it.
Undeadartist:
I didn't change any of your line work or perspective since Juto already helped you with that. I thought i would give my input on the rendering of the character and the actual painting part.
The image you posted seemed to only be painted in value shifts, so for dark areas you had black, and for the light areas you had white. Then you had the really bright and saturated aqua blue for the light source under her. To add more depth to the image i added some color, but i also used saturation shifts and hue shifts to the colors, not just value. I'll explain more further down.
I tried to keep all the colors desaturated and grey to keep with the original image you posted. But you have to keep in mind painting with black is something you want to stay away from.
For the star on the bottom:
I think you had the bottom way too blown out, which takes away from the strong impact you wanted. If you want to make something really vibrant and bright, you need to adjust the temperature of the color. I just adjusted the left half of the star so you can see what the difference is.
Color Temperature- So something to keep in mind when rendering a painting is how light effects color. If something is really bright then you want to raise its value and shift its saturation. The closer something is to a hot spot, the less saturated and higher value it is going to be. If you notice for the star, i made the base area around the line of the star a dark saturated blue. Then i made the actual starline higher in value and shifted its a hue a little bit to more of an "aqua". The center of the line is almost white. This will make your 'magic' light pop, as well as anything else you want to pop and be bright.
For the effects of the star, i just duplicated the starline, motion blurred it. Then manually i painted streaks of light. Then messing with the brush settings, i used scatter/shapedynamics/opacity jitter, i painted the additional streaks coming out.
So keeping color temp in mind, i painted the base skin tones as well as the clothes. So for instance, the skin- i went with a normal peach skin tone. For the bright spots of the skin, the color desaturates a little and goes up in value. If its at a darker spot, then the value goes down and the saturation goes up. Same for the clothes.
I just did a base of the colors so you could see it, of course you can change the colors and give her more pale skin. Just remember to work with saturation, hue, and value; not just value alone. Colors don't just turn to black or white, once your start to work with color and light it will make painting much more easier. Hopefully this helps you with your work. Sorry if there are typos, its 330 am here.