When I was a kid, my school and public libraries always had a limit of how many books any single person could check out. Since it only took me a few minutes to read a picture book, I made the jump to chapter books a few months into first grade.
I think that my early reading habits made their mark on my writing habits. While I’ve tried my hand at a few picture books–often so that I could attend the SCBWI Missouri retreats with a focus on picture books–I’ve completed more manuscripts for novels than picture books. And actually, my agent has assured me that those projects for younger readers are short stories.
Don’t get me wrong. I adore picture books. But I immerse myself in novels.
Kristin Wolden Nitz 
I know I love picture books too. I used to think I just loved children books. I recently found out that my love is really picture books a form of children books. Wow it is way to late for me. But anyways.
http://www.examiner.com/x-5291-Picture-Books-Examiner~y2009m3d10-What-is-a-picture-book
When I first started writing, I felt like I was “supposed” to write short stories first. But I hardly ever read short stories! I am definitely not a big fan. It felt very daring to presume to write a children’s novel — but that’s the kind of book I like to read most, so it’s the right book for me to write.
You can learn things about structure by writing short stories. With every 800 words that you write, you need a beginning to hook readers into your world and an ending that will ease them out. That can be good practice. But I too prefer writing the form that I like to read: Novels! Write what you want to read is a classic and excellent piece of advice.