A lot of thought went into this, and it shows in the nicest possible way.
From the little heat-wave emanating from the pristine cup to the mysteriously shrouded background, it's a keeper.
Having multiple sources of light would help you capture the steam coming from the coffee. I've seen people use lights from a blind to highlight sections of it and give an intense focused light in bands for an interesting visual appeal.
What is it about smoke and steam? So alluring. I like your low key approach. Just my opinion (which means absolutely nothing LOL) I would have made it more in the left corner, with more negative space to the right. No big deal. I'm just thinking out loud. :) 7