Frank Palumbo and his students kept up a correspondence with Bradbury for a decade or more, and Frank kept not just Bradbury's letters, but the envelopes they came in. Thanks to Frank's generosity, I am able to share some of them with you here.
One or two items have been tidied up a little (by me), mostly to remove folds, creases and inkblots. (The whale above is one of my Photoshop efforts, but you can see the untouched Bradbury original below, with the original message.) The most common items in the Bradbury doodle repertoire are faces and animals. The humans sometimes look angry, sometimes perplexed, sometimes just grotesque. The animals are a bit more straightforward.
The last item is a simple Bradbury annotation of the Edgar Allan Poe postage stamps on the envelope, indicating Bradbury's idea of the familial relationship between the two authors.