Preheat oven to 350 degrees.
Prepare pasta according to package directions.
While pasta is cooking, saute beef in a large skillet until browned; drain well. Add taco seasoning mix and water; simmer for 5 minutes, or until thickened. Add beans and cheese. Cook until smooth and well blended. When pasta is done, drain well. Fill shells with beef mixture (1 to 2 tablespoons per shell).
Combine Picante sauce and tomato sauce in a saucepan. Cook until heated, stirring occasionally. Spread 1/2 cup of the sauce over the bottom of a 9- x 13-inch baking pan that has been coated lightly with olive oil.
Place filled shells side by side on top of sauce; pour remaining sauce evenly over shells. Sprinkle with olives. Cover with aluminum foil; bake for 35 to 40 minutes, or until thoroughly heated. Sprinkle with green onions. Cover and let stand for 5 minutes before serving.
Garnish as desired.