There's something perfect about the backwards tonality, highlighting the focal point. I'd have probably made a mediocre sketch using the other way around (more detailed foreground) and not had this amazing impact. See how you have to unlearn!
The sketching and shading is messy, as if the drawing was done with urgency. This raw, jagged style creates a sense of energy and an ever-changing quality, which is lost in perfect, overly planned sketches.