My commissar has a big tank and a big flag (thanks to a certain mammalian for the flag design). All Imperial guard armies need a commissar to ensure loyalty, dedication and accurate fire. The "Bonestorm Brigade" is pictured above.
Commissar is the term used to designate a political officer in the Regiments of the Imperial Guard. Commissars are tasked with the duty to maintain the morale of the troops during their massive campaigns, often in the face of staggering casualties. The Commissar is empowered to use any means necessary to ensure the loyalty and moral purity of his or her charges, and is regarded with a mixture of fear and admiration by regular Guardsmen.
I think a commissar has more authority with a big tank than without one!