Yer Bugger! Hear me I begya and say thankee. (Jesus, those books are getting to me)
Well, you can find some all over the net, but here is what i really think you should do: One of the big rules of art is color theme/contrast. You need some sort of dominant color in there, and then use either shades of that, colors next to it on the color wheel, or color opposite it on the color wheel. I suggest you first color your marine like so, and once you've done that use those colors for the rest of it. Then, take a very simple map, just a black outline, and color it, shadow, bevel it, add all the effects you want! Make it all your creation!
Do as you please deathlegionnaire-sai, but hear i begya. | 
