Reach the indicated level to unlock the costume in Multiplayer mode:

Basic costumes: Level 1 
Third pattern for basic costumes  - Level 10 
Third pattern for Gale            - Level 50 
Third pattern for Hero            - Level 80 
Third pattern for NEVEC           - Level 65 
Third pattern for Stranger        - Level 35 
Fourth pattern for basic costumes - Level 20 
Fourth pattern for Gale           - Level 60 
Fourth pattern for Hero           - Level 85 
Fourth pattern for NEVEC          - Level 70 
Fourth pattern for Stranger       - Level 40