Short answer: nope. We supply the words and art; you supply the ideas.
Longer answer: Storybird is about creative constraints. We purposefully trim away dozens of features to keep you focused and having fun as you write stories or make poems. So we don't offer art uploads or text input for poems as a way to make the app surprising and inventive. By imposing these constraints, your brain creates connections and ideas that you otherwise wouldn't have. And that's cool.
The exception is that teachers may use custom word lists for Poetry associated with an assignment. Read more here.