Issue 39 of Fantasy Artist includes a fantastic tutorial on creating a classic heroine in the style of the great Frank Frazetta. It walks you through the whole process, covering colour treatment, paint application and composition.
Often, a great idea is not the first idea that comes to mind – even Frazetta had roughs. Start small, sketching out compositions the size of a box of matches until you’ve found something you love. The mind registers value (how light or dark something is) before colour, so many find it helpful to save that planning for the next step.
Now, it’s time to explore a colour scheme. You’re working small, so this is the best time to experiment. Do golden hues make it feel majestic? Does red evoke the feeling of fire? As long as you stay true to the values and composition of the thumbnail, things should start to take off.