@ArtistErin Hi! Your illustration is lovely; it has the warm feel of classical kid's books to it. 
I started a book because of an illustration, and a few of them, actually. The funny thing is that the illustration that sparked my idea never made it into the story.
All I did was ask questions.
For example, this one is behind my very first picture book.
I asked, why is the girl so sad?
Well, she just cut off her hair.
Why did she do so?
It was probably too long. Maybe waaaaaayyyyy too long, so it caused her a lot of problems.
What kind of problems? Well, maybe animals got stuck in it all the time.
(At this point I did a quick sketch, that did make it in the final book!)
Did she like the result? Probably not, she's lonely now, without all the animals...
And so on... until the whole story was born. It took many rounds of edits and re-thinking.
For me, starting with an image feels natural because I tend to tell stories in images. I think it's the same for a lot of illustrators, we tend to go with illustrations first, and words... not so important. Haha.
But every story idea needs a lot of work and a lot of questions. Don't be afraid to start over and over and redo the whole plotline if it doesn't feel just right. Do some more doodles from the world of your story.
Good luck!
