thanks for your comment!
well.. there wasn't a concept i was working after. i started with the dancer and when he was done i just added the other parts. it's like looking at the picture, imagine a new part/change, and then bringing it "to paper". the picture evolves until i decide it's finished.
of course that's not the way i ALWAYS work. but it's the story of this pic.
choosing colors for me is a matter of trial-and-error. the best way to find a good color is opening the color/gradient editor in your software and look at the influence the different colors have on your work. sometimes you have to tweak a lot to reach the desired goal (as it was with "dancing" btw), or you might randomly select a color and "baamm"! that's it! heh
the best way to "develop" a good picture is either -make a good concept/sketch- or -try to imagine the pic while drawing it-. i don't think it helps much just to start drawing random things an hoping that a good composition will evolve from that. you should always have a plan in mind, be it the plan of the whole image in form of a concept, or parts of the image cleary built in your imagination.
i am not a big friend of concepts, cause my concepts always change a lot while working on a picture. so i am more of the imagination-guy.. you should be able to work out a specific concept though. but i've got enough of that at work.. *g*
i hope, that helped a little, and hey.. it's only my opinion. other artists might work completly different. try it and judge for yourself.