What is a fashion storyboard?

From my understanding a fashion storyboard is when someone already has a feel for what they are showing and they just organize the board in the manner they want to present it. If that's not what you meant then i would take a couple of steps back to the thinking process and start a mood board. That is when you take various things like fabric swatches,colors, diffrent textures, prints and everything else that inspires you to think about what you will be presenting. Mood boards usually have illustrations as well. The only thing is it all has to be cohesive and represent the type of feel you are going for.