Though they look short and simple, picture books can be challenging to write. I know that first hand, from replies I've received from agents.
"...I especially enjoyed the humor and know that the illustrations will expand in greater depth visually. Overall, this is entertaining for young readers.Here's where the but comes in:
"When considering your story further, I'm wanting more suspense in the beginning, a tad more tension with higher stakes in the middle, and more depth in the end. For plot I'd like to see more character growth . . . "Don't misunderstand me. This personal reply is very encouraging. But I want to reply, "Hello, I've read so many non-exciting picture books with no plot or . . . ." well, you know what I mean. It's a tough business, but one I find exciting.
My suggestion for you is to read lots of picture books to see what's being published. Some books will make you chuckle and marvel at an author's creativity; you might even consider that he/she is totally out of your league. But other books will cause you to shake your head. That being said, I still recommend you read and find authors who inspire your creative thoughts. Sometimes writing is in your blood. You've got to do it! If that happens to be how you feel, I understand.
I will be posting picture books that match my style and ones that I hold up as examples of good writing. I will also share some great articles to guide you through the writing process.
You may want to look at the picture books I've recommended in the past, as well.