What are the various concepts of Heaven in Christian theology?
As stated above, concepts of Heaven vary among different Christians. Perhaps the greatest variation is between actual Christian theology and popular devotions and imagery. The starting point is often the Epistles of St. Paul:
So also is the resurrection of the dead.
[The body] is sown in corruption; it is raised in incorruption ...
It is sown a natural body; it is raised a spiritual body. (1 Cor 15. 40-44)
This notion of a spiritual body is the key point. Physical bodies are part of space and time, subject to change and decay. The Greek of St. Paul suggests that the spiritual body, and heavenly realm, are incorporeal, and do not exist within time or space as we conceive of them in our physical bodies. Thus the experience of humans after death, like the viewpoint of God, are completely different from those of living humans, and incomprehensible to us due to our limitations as spatio-temporal beings.
This causes a problem for iconography -- for paintings or even descriptions of Heaven. If Heaven is alien to the way we think and the language we use, we cannot talk about what it is actually is. All we can do is construct analogies, based on our own ideals. Those analogies all differ, but they all fall equally short of a reality theologians agree is beyond our comprehension.
This question is a difficult one because many views of heaven exist. The view often subscribed to is one of a light filled place in the presence of the Almighty which would be all that one would need. Singing seems to be voluntary praise on earth to a God who needs nothing like singing in heaven. Sitting in the presence of the All-Knowing God would be enough for a mere sinful mortal, knowing that heaven is the ultimate achievement for believers. Earthly relationships would pale in comparison to a relationship with God, so it seems that if there are earthly connections still, their importance would be less than they are on earth.