Checkerboard Cheese Sandwiches

INGREDIENTS

• 1 (10-ounce) block extra-sharp Cheddar cheese, grated
• 1 (10-ounce) block Swiss cheese, grated
• 1 1/4 cups light or regular mayonnaise
• 1 (4-ounce) jar diced pimiento, drained
• 1 teaspoon dried onion flakes
• 1/4 teaspoon freshly ground pepper
• 20 thin white bread slices
• 20 thin wheat bread slices
• Garnishes: grape tomatoes and black olives, secured with wooden picks