In order to understand the significance of the contrast between the two pictures, it's important to get an overview of the entire story.

"Soldier's Home," by Ernest Hemingway, tells of a soldier named Harold Krebs who comes home late from World War I to a town in Oklahoma. The townspeople no longer want to hear about the war, and, after a while, he no longer wants to talk about it. He becomes listless, sleeps late, and wanders around without knowing what to do with himself. He enjoys looking at the pretty girls but lacks the energy or courage to pursue them. In his mind, he contrasts the girls in his home town, who are prettier but harder to get, to the French or German girls who were not as attractive but easier to befriend.

When Krebs sits on the porch and wishes that the book he is reading had more maps, it is obviously a reference to the fact that he has no direction in his life. When Harold tells his mother that he doesn't love her and he's not part of God's kingdom, it's an indication of his dislocation. In Hemingway's spare style, he uses these details to show how much the experience in the war has affected Krebs.

In the first two paragraphs, Hemingway gives the description of the two pictures as an overview of the entire story. In the first picture, Krebs is in college with his fraternity brothers, and they are all wearing exactly the same collars. This shows that Krebs fit perfectly into society—just like everyone else—before he left for the war.

In the second picture, Krebs is in Germany; his clothes don't fit properly, and the girls aren't very pretty. This highlights his dislocation. He is in a foreign country—far from home and away from the society in which he was raised. When he comes back, he can't fit in anymore.

"Soldier's Home" is yet another short story by Ernest Hemingway detailing the experience of returning World War I veterans. Harold Krebs fought in many of the important military engagements in the war and comes home to his small Oklahoma town an obviously changed man.

In the first paragraph Hemingway describes a picture of Krebs with his college fraternity brothers before the war. The description focuses on the rigid uniformity of the men:

There is a picture which shows him among his fraternity brothers, all of them wearing exactly the same height and style collar.

There is a perfection in this picture. Young men all looking the same on the eve of a great war where they will go off and perform heroically. It is an emotionless picture which cannot predict the horrors that war will bring.

In contrast, the next paragraph describes a picture of Krebs with another soldier and two women. It is much less than perfect. There are no medals showing (in fact the men look disheveled), and the women are not the beautiful creatures befitting heroes. Even the Rhine River, which is part of heroic myth and folklore, is not in the picture. Instead, Hemingway describes two very ordinary men who have not performed heroically. 

Later in the story Krebs is unable to tell anyone about the atrocities of the war. Instead, they only want to hear heroic tales, which are lies. Those in the town will accept nothing less than the perfection detailed in the first paragraph picture. They want life to return to how it was before the war, and for men that conform to a particular ideal. Unfortunately, Krebs has been through too much and feels like an outsider, revealing that "Soldier's Home" is an ironic title because Krebs no longer feels at home.