Any quilt block can be made as calm or as wild as you would like it to be. It's all in the fabric choices.
Just using two colors make a quilt seem calm. I made our daughter a blue and white quilt last year that turned out lovely. I used Eleanore Burns "Tennessee Waltz" pattern. It was easy too, a bonus!
Also, check out http://www.quiltville.com/ She has many beautiful, fun patterns to make. Perhaps your grandmother would like a scrappy quilt. Always a good choice.
Bottom line, your grandmother will love what ever you make just because you cared enough to make it especially for her. Grandmothers are like that!
Have fun with your quilt making. It'll show in your work. Trust me!