Imagination ?????????

When I was little, I loved cycling in a small three-wheeled bicycle I had. I could paint auto rickshaw, peacock, a small home with a lake or river infront of it, hills in the background, a sun partially hidden in the hills, a tree by the side of home. This was the extent to which my imagination would go at that time. Everything perfect. what is the source of imagination? our knowledge? our experience? or what? Since imagination is a noun can we add an adjective such as good or bad to it?