I was an odd kid. I don't know if you'd call me imaginative so much as creative though.
I was unhappy unless I was working on something at all times. Sometimes I'd write stories and draw pictures around the words, then I'd color and bind my pages into little books and give them to my parents at bedtime to read with me. Then when I was eight or so I became obsessed with polymer clay for a while. It was expensive though so I had to make everything in miniature: miniature lions, miniature motorcycles, tiny little flowers, and sometimes minuscule people but mostly small animals.
Lastly, I used to play this game where I'd close my eyes and imagine scenes that I knew, like my old house, and I'd try to reverse north and east in my mind, so that the sun would rise and set in a different direction, affecting how light fell on everything.... people generally don't understand when I try to explain this, but I would try to see how long I could keep a visual concept of this sort of complex scene as I walked down the street in my mind.
I also was pretty good at guessing how something would look from the sky for some reason. I got pretty good at impromptu maps, even when I was very young.