The first thing that springs to mind is, "This feels like it's straight out of a movie." It's very dynamic, with a lot of tension.
The background is kept simple, but gritty and in keeping with the overall mood. I think adding to the background would detract from the picture as well. The shadowy-ness is appropriate and well-done, but I am curious about the light distribution around the spanner - there doesn't appear to be any shadow cast down from it on the "floor?" I am not sure whether or not this is deliberate, but it's not a big deal. The hanging wires draw the viewer's attention vertically down to the central figure, and the fact they match Hackley's dreadlocks is a stylish touch. :cool: The colour scheme as a whole, in fact, is really nice: soft, earthy khakis and browns with dashes of vibrant red that really bring the scene to life.
I really like the character idea - tomboyish nerd girl-types are relatable but interesting characters with a lot of scope for exciting plotlines. It would be good to see more of Hackley.