In "There Will Come Soft Rains," how does the author describe the nursery and what is significant about the way the nursery is decorated?

The first description of the nursery is that it "glowed." The nursery walls are lighted with images and films and this is the source of the glow. But Bradbury might be comparing this glow to the radioactive glow of the town following the atomic blast. The point here is to show the dangers of irresponsible uses of technology. It is technology that has created this virtual world of the nursery but technology is also responsible for the atomic weapons. Both the nursery and the aftermath of the bomb create an artificial, superficial glow, both inauspiciously fake and unnatural. 

The films on the glass walls "lived." This is also a subtle critique of technology. The glass walls "live" on but the people have been killed. What keeps the walls alive (technology) has also led to the deaths of the family. It is therefore, ironic to say that the virtual, inorganic walls "lived." Initially, the nursery walls are "alive" with signs of life. "Animals took shape: yellow giraffes, blue lions, pink antelopes, lilac panthers cavorting in crystal substance." The nursery gives the appearance of life. The reality is that all life has been snuffed out by the bomb.

Closing the description of the nursery, the narrator adds "It was the children's hour." This means that the house and nursery were programmed at this certain time in order to let the children play in this virtual world of animals and meadows. But the phrase "children's hour" has sinister connotations as well, since it can mean the hour (time) of the children's deaths.