The Inspiration: Max Fischer in Rushmore
Essential Elements: Oxford shirt, black-and-red striped tie, prep school blazer, pins denoting various honor societies. Braces. Glasses (NOT hipster glasses; this is Westchester*, not Bedford Ave., you monsters). Some acne, though don't overdo it.
Key Accessories: A red beret would be nice. A smaller, younger acolyte. Perhaps a sash denoting a club membership.
The Attitude: Enthusiastically and magnanimously superior. Age-approprately petty and jealous. Ambitious to a fault.

*Yes, yes, it's not necessarily Westchester, but rather a vague Wes Andersonland. Fine.

The Inspiration: Gideon Graves in Scott Pilgrim vs. The World
Essential Elements: Red button-down, black tie, white blazer, white pants. Glasses (these can be hipster glasses, fine). Shag wig.
Key Accessories: Cell phone. Some kind of flaming sword.
The Attitude: Predatorily superior. A king in a made-up kingdom.

The Inspiration: Jack Whitman in The Darjeeling Limited
Essential Elements: Semi-fancy vintage pajamas. Bright yellow robe, preferably borrowed/stolen from a significant other that you left at another, shorter party. Mustache. No glasses.
Key Accessories: A bindi. A flower wreath. Slightly shabby but ostentatiously old-fashioned luggage. Two marginally more fucked-up brothers.
The Attitude: Amiably superior. Obsessively pining for a lost love, yet also attentive to the romantic attentions of others. Competitive with siblings/friends.

The Inspiration: Louis XVI in Marie Antoinette
Essential Elements: Powdered wig. Fancy tricorn hat. Cravat after cravat after cravat. Basically, your standard 18th-century French aristocrat/monarch costume.
Key Accessories: A goblet of wine. A date who you cannot possibly keep under any illusion of control. Preferably a close relative to invite you to the party to begin with.
The Attitude: A bemused superiority. A terrified attitude towards sexuality. A weary acceptance of your future beheading.