Costume design is an integral component of any "period" film -- a film that takes place in an earlier period of time when apparel was distinctly different from what is worn today. It is questionable whether the phrase "lavish costumes" is appropriate in the case of a war movie where the overwhelming majority of characters are dressed in military attire. To the extent that any film director and his or her costume and set designers wishes to accurately reflect the time and place in which the story occurs, however, careful attention is paid to the details to make sure that every item of clothing, and every ornament on those clothing, are appropriate.
In "Saving Private Ryan," director Steven Spielberg placed great emphasis on historical accuracy and, as is common in the production of films, kept technical advisors on the set to ensure that the characters, dialogue, and actions were all accurate to the time and place depicted. Costume designers working on period films routinely consult illustrated histories of the eras in question, perusing photographs, drawings and paintings to get ideas on how to design the costumes for the films on which they are working.
On a film depicting the war against Nazi Germany, with German soldiers prominently displayed, the mere use of the grey attire and German Army symbols like patches and commendations that were worn on the uniforms, could not help but denote the grim specter that was the pride of Hitler's Wehrmacht. Swastikas and the ubiquitous Iron Cross, enduring symbols of German militarism of the past, are certain to evoke images of evil.