I concur with Why so Cereal?
To me it represents Batman watching over Gotham but also the sagging shoulders and lowered head indicate the huge responsibility he bears.
In DK there's a tiny piece that made me sit up and say "that's Batman". It's the bit where he tries to cut into Scarecrow's van only to be bounced off a pillar. He just gets up and walks over to the barricade, climbs on it and waits to jump. Not a brush-down, shake of the head, crack of the neck, stretch, moan or gritting of teeth. Just gets up and finishes the job without complaint. That's Batman to me.