Here are a couple of exercises to further stretch the expressiveness of your body and voice. Do these in a group or individually. There are many other games that you can play to exercise your imaginations. You can look in the library for a book of theater games.
Pretend to be an animal in the jungle. Think about how it moves fast and sneaky, or slowly and majestically, with heavy footsteps or on dainty tippy toes, slithering, hopping, swinging, or creeping? Every animal moves differently. Use your whole body, not just your arms and legs. How does the animal move its head? Its chest? Its tail? How does it stand when it listens to a faraway sound? How does it grow sad or angry or happy? Now, make sounds to accompany the animal's movements. Finally, move across the room to the watering hole and take a drink. On the way, get scared, get angry, make a warning sound, or stop and listen if an enemy is near. Your journey to the watering hole is like a story told, not with words, but by your body and voice.
With masking tape, make four squares big enough to stand in. Label them Fear Pain Love Anger. Try telling "Monkey Steals the Drum" and move from square to square, matching the feelings to the labels as the feelings change. Remember, there are many levels of feelings. Fear can be hearing the monster coming near, or being shy on the first day of school. Pain can be cutting your finger, or getting your feelings hurt, or being disappointed. Love can be kissey face, or kindness, or caring for a pet, or feeling proud of yourself. Anger can be revenge, jealousy, meanness, teasing, or the feeling of determination that we have when nothing can stop us. And there are many, many more. There is no right or wrong. Don't worry if you end up jumping from box to box. This is a stretching exercise.
The imagination is like a muscle. The more we use it the quicker and stronger it gets. Don't be discouraged if at first you feel awkward. Keep trying and soon you'll be leaping and roaring. Just like roller blading, bike riding, gymnastics, basketball, or any other skill, the more you do it, the better you get at doing it. Practice playing, and soon you'll see your storytelling skills growing.