This shows the excess above what is predicted. The brownish regions are all bright areas which have been truncated.
Several features are evident.
There are localized bright spots, corresponding to individual gamma-ray sources. We also see the band in the inner Milky Way, corresponding to a fairly bright excess from the Galactic plane. Finally, there is the gamma-ray halo, which appears in shades of blue. Perhaps the biggest surprise is the apparent size of this halo. There has been some previous discussion of the possibility of a gamma-ray halo, but not of the size seen in this image.