Dawson and Downey
Dawson and Downey are symbols of protection (as marines) and prosecution (the murder of Santiago). This is used to create a stark image in viewers' minds to underscore the moral dilemma some of the characters face in the film.
The Hero
Reiner evokes imagery of heroes and heroism when framing Lt. Kaffee, who is fighting to convict Private Santiago's murderers.
Code Red
Reiner and Sorkin use the oft-discussed Code Red order (particuarly the color red itself) to evoke harsh images of death and violence.
Guantanamo Bay
Reiner uses the specter of Guantanamo Bay to create harsh, violent, and murderous images in audiences minds.