Aww shucks. Thanks for the compliment.
But yes, it's one of the uncommon times that I came up with that on the spot. Emotion and imagination played a big part in the making, mostly because I was impressed by the picture and tried to describe the scene as best as I can. There's no set way to do it.
Read as many stories whether from professional writers or hobbyists, learn their unique writing style to improve your own. It's a neverending journey and these skills don't come overnight. Also, lots of practice by writing your own stories.