Revelation 21 gives us the most vivid picture of what heaven "will be like". Outside of the cosmetic aspect of heaven, we will be worshiping. We will also have certain responsibilities in heaven such as judging angels (1 Corinth. 6:3). Many people believe we will tend the garden as well (since it was our original responsibility).
As far as people dying and "seeing a light" who knows? If God allowed glimpses of heaven to be seen, that would be his call. I personally do not believe that people in heaven (or hades, whichever you believe) cannot see us (people on earth). I believe through scripture there is no more sadness in heaven. If people could "look down on us" they would be very sad to see our daily lives full of sin.