"Have not come up with a design yet for the rainmaker."
Yes, I understand that perfectly. A rainstick (not a rainmaker - it's not supposed to make rain, just sound like rain when you play it) is not only a piece of artwork, it's a usable piece - one that will be more visible due to its use. So the decision as to what will engraved on its surface is important, relatively speaking.
My suggestion is to take a walk, either in your mind or in the flesh. Go to places you don't ordinarily go to. Look at nature, at buildings, at people. Put yourself in a receiving mode. You are a recorder of life. Look at overall forms of what you see. Since the rainstick is elongated, you might want to pay more attention to long things in your environment for creative stimulus. Look at tree trunks. What shape are they; how are they patterned; how are they colored; what are their irregularities that especially take the eye? Look at noses. Look at birds in flight. Just open yourself up to these inputs.
When you open yourself in this manner, you accept your potential for creativity. You accept that your imagination is a very important part of who you are . . . no matter where it might lead you . . . no matter what emotions or thoughts might arise in the process. Let them come and go as they will. Accept yourself. Let those thoughts, images, imaginations rise and recede. Try not to block any of them. They are all part of you and should be accepted. Let the environment flow into you, into your creative spirit. As you continue your walk, you might want to take notes so you don't forget everything you see. Along the way, something may come to you that will fit, something that you know is RIGHT for your project. Hurry home. Sketch it out on paper or directly on the gourd surface in pencil. Now, the interchange of your spirit, your energy and the energy of the gourd has begun.