Shortly after the storm, I discovered that there was a blog being maintained by some people that were still in New Orleans, staffing a data center. They have also been out and about, taking pictures of the casualties.
When you first look at this photo, you see the water lines on the car, and realize how high the flooding got. But look beyond the car, to the building. Not only do you see even higher water marks, but there is an orange X on the building.
It’s hard to make out unless you look at the large version (474k) of the photo, but under the X, there is the number 6.
This is from the searchers in the city. A slash means all clear, an X means bodies found. The 6 is the number of bodies.
This picture taken from this gallery. Many more photos here that express the magnitude of the event.