This image is a "heat map" of the Valhalla map. It is an example of data samples taken from games during the beta that show where the choke points and hot zones of a map are.
The more red an area is, the more kills that have happened in that particular point. The heat maps are used to see where changes to the level's layout, spawn points, or weapon locations need to be made.
As the beta winds down, changes will be made based on the 40 million games played so far.