Here's my entry to Project: Rooftop's Storm redesign contest. My first thought was to make it where whenever Storm is using her powers, her hair kind of comes alive and becomes this crazy, living storm cloud. I tried to convey that idea here, with varying degrees of success.
When it came to her costume itself, I mostly tried to keep it sleek and basic black, with silver highlights. The lightning bolt design on her chest let's you know what she's about (if the crazy hair and lightning bolts flying from her eyes and hands didn't already tip you off), and the flowing cape lends itself to the "living cloud" concept.
My weak attempt to illustrate her in cloud-form. Though I'll admit, this illustration was a little rushed!