Downloadable content is official content released by Paradox Interactive. There is two major expansions and a bunch of aesthetic DLC.
Major Expansions
A House Divided
Heart of Darkness
Minor DLC
Interwar Cavalry Unit Pack
Adds unique models for armies using cavalry units in the interwar period between WWI and WWII. It was released on 2013-09-30.
Interwar Sprite Pack
Adds updated uniforms for the interwar period between WW1 and WW2. It was released on 2010-11-02.
American Civil War Sprite Pack
Adds 12 historically authentic modeled units for the 「American Civil War Era」 with new animations. Units are equipped with muskets, sabres, kepis, hardee hats and much more. It was released on 2012-07-31.
German Unit Pack
Adds updated uniforms and units for German soldiers. This includes units and uniforms for the German Empire, North German Federation, South German Federation and Prussia. It was released on 2013-04-22.
Interwar Artillery Sprite Pack
Adds unique uniforms for armies using artillery divisions in the interwar period between WWI and WWII. It was released on 2011-03-15.
Interwar Engineer Unit Pack
Adds unique uniforms for armies using engineer divisions in the interwar period between WWI and WWII. It was released on 2013-04-22.
Interwar Planes Sprite Pack
Adds unique uniforms for armies including airplanes during the interwar period between WWI and WWII. It was released on 2011-03-15.
Songs of the Civil War
Adds nine minutes of music to enhance the atmosphere of Victoria II. It was released on 2013-04-22.