What do the silhouettes on the wall suggest about the family?

In "There Will Come Soft Rains," the silhouette on the wall is the most haunting image Ray Bradbury presents because it shows the instant a nuclear blast killed the unsuspecting family. Each member of the family was in the middle of some activity: the father was mowing the lawn ("the silhouette in paint of a man mowing a lawn," the mother was gardening ("Here, as in a photograph, a woman bent to pick flowers."), and...

In "There Will Come Soft Rains," the silhouette on the wall is the most haunting image Ray Bradbury presents because it shows the instant a nuclear blast killed the unsuspecting family. Each member of the family was in the middle of some activity: the father was mowing the lawn ("the silhouette in paint of a man mowing a lawn," the mother was gardening ("Here, as in a photograph, a woman bent to pick flowers."), and a boy and girl were playing catch with a ball ("a small boy, hands flung into the air; higher up, the image of a thrown ball, and opposite him a girl, hands raised to catch a ball which never came down."). 

This image helps Bradbury develop his theme that nuclear annhilation will destroy everyone. And that this annhilation can happen at any time.

This image also helps explain the absence of people in the house. It explains why the food the house makes goes uneaten and the cards go unplayed. In addition, the absence of people makes the house meaningless. 

In general, this idea of a silhouette after a nuclear blast comes from reports of nuclear shadows on walls after the United States dropped atomic bombs on Hiroshima and Nagasaki.