In a large pitcher, combine lime juice, pineapple juice, and ginger.
Cover and chill for 2 to 24 hours.
Strain mixture to discard ginger
Slowly pour ginger ale into juice mixture.
Serve over ice in chilled glasses.
Garnish with lime slices.
Dress up the punch with citrus ice cubes (optional). To make these decorative cubes, fill the compartments of an ice-cube tray with lime, lemon, and/or orange slices (halve or quarter slices to fit). Fill with water. Freeze until firm.