I know what I look like, but I can't come up with a ubiquitous image. I ride in full kit on a vintage touring bike with rack and panniers, no reflective vest and only one front and one tail light, most of the time with a helmet, no mirrors. A friend of mine wears normal pants, a cycling jersey, rides a cross bike, occassionally a reflective vest. Some of you ride folders, some wear the clothes you will wear all day, some wear noncycling specific athletic clothes, some wear full kit, heck some of you might go nekkid.

My point is that there isn't a single "right" or "wrong" way to look like a commuter, all one needs is a bikr and a destination. In those terms, there isn't a single thing any of us can do to NOT look like a commuter unless we stop cycling.