In a large bowl, combine chicken, celery, apple, and bacon.
In a medium bowl, stir together sour cream, mayonnaise, and lemon juice. Add to chicken mixture; stir to coat. Season to taste with salt and pepper. Cover; chill for 2 to 24 hours.
To make tombstone sandwiches, spread chicken salad on half of the bread tombstones. Top with remaining bread tombstones . Spread the edges of sandwiches with cream cheese and roll edges in pecans to coat. Use cream cheese to stick tombstones to plate. Add purple kale for a creepy groundcover. Makes 14 tombstones.