Since speculating what Cinder's face looked like proved too easy, I decided to go hard and try to guess what everyone's alternate attire looks like.
Given the white theme everyone seems to be going with, I simply gave her a white shirt. Incidentally, her corset and black skirt remind me of Goodwitch's attire. Aside from the boots, this is pure speculation.
Saw the buttons and thought, designer jacket
(not friggin' military jacket and cape bullshit).
Well, we know she has a white shirt with rolled up sleeves, complete with the arm ribbons. What we don't know is what she's wearing on her lower half - but I figured it had to be black and provide plenty of free movement. I added a little something to appease the Bumblebee fangirls.
Everything's confirmed, no thought went into this one. Before you comment that it looks like she's wearing shorts, that's just a very poorly drawn, tight fitting skirt.