Southwest has been doing special state-themed liveries for quite some time now, and the latest one is for the state of Louisiana. A bit of explanation might be in order: the Louisiana state bird is the Brown Pelican. This B737 is painted similar to the Louisiana state flag, which features a white pelican with a nest of three chicks. Union, Justice, Confidence is the Louisiana state motto and also appears on the state flag and seal.
Here's a bonus shot for Filip, who asked recently about the blast fence at the west end of Runway 24 Left. This is how that end of the north complex appears from the tower. As a double bonus, you can also see the current state of the construction on the Midfield Satellite Concourse:



