Much of the creative preset, that accumulates over a lifetime, starts in the childhood, sure - as soon as we start to develop the appreciation for joy, that colors, music, movement, poems and words bring to us.
I won't be surprised, if for you, too, it was the fairytale and adventure world, that books were responsible for, thankfully! ;)
These are illustrations to different Russian fairytales, by I. Bilibin, who has done plenty of similar work, drawing for children's books... I remember spending hours letting my imagination flow with daydreaming about mystical dimension, that a fairytale is ;)