When I look at children, they have the most amazing imaginations and creativity. They really do have an innocent and unyielding love. They love to play and make things, explore and enjoy life. Their youth brings life to all who they meet (upon seeing a baby, who doesn't look at him or her and get and instantaneous feeling of life and joy?)
I really think there is another reason Jesus was always saying that to get into heaven you must be like a child. I think that God might be much more like a child than we might think. To be greeted by a child when we die would not be what most of us would imagine. A child meeting a child would probably say to them, "Hi, my name is _____. What's your name? Do you want to go play?" Their innocence allows them to have no walls between them and others. An adult would most likely look at a child and wonder, "Who is this kid? And what are they doing here alone?" The child will accept God as a child much easier than the adult will.
The main reason I think that God is more like a child than our other images is that no one, other than a child, has the creativity to create what God has created in this world. But I guess the reason that God is child, father, mother, grandfather, grandmother, husband, wife, sister, brother, friend, savior, redeemer, comforter, etc. is because he IS all those things and more. We see in God what we need to see or perhaps even be at that particular moment. So, maybe God is trying to tell me to lighten up and be more like a child. I am, after all, a perpetual child in his eyes, so why not embrace being one?