One of the questions that Ann Whitford Paul asks you think about your picture book (in her fabulous book Writing Picture Books) is: Can your book be used in the classroom? In other words, are there concepts in it that may fit in with a curriculum. You may accidentally have this component in your story, or you can start with the learning concept and build from there. And starting with the concept may just provide you with some needed inspiration!
So how do you know what they are teaching and at what age? School standards! I wanted to write a picture book for the kindergarten set, but I was having trouble coming up with an idea, so I pulled up my state standards, found a math concept that they want kindergartners to know, and built a story around it. And the nice thing is, you can use the standards from any state. You are just looking for a general idea to get you going. I found the Indiana standards to be pretty helpful, so here is that link. You can pick a subject and then pick a grade level and it will pull up a printable version of the standards. Explore and generate some new ideas! A picture book is one of the most valuable tools for any teacher.
Side note: While I did not win the Storybird contest this weekend, I want to thank all of you who voted for my story! It was fun to have a short little story out there that people were reading. My first taste of an audience for my work! Thank you!