I imagine a young boy or girl standing in front of the window. Their back to the viewer lit mostly or only by the window. Looking up at it, they are deciding if they can pass through it like a door to the world illustrated in the glass. I think they can... But I could be wrong. It may be that if the person ran and jumped through the window they would just go through it and get cut up and fall to the ground breaking their back and scull... But I think the first possible story is better.
I like the first comp of this image better too.