Just had a bit of a "compare and contrast" with a friend, and despite 100% trophy-ing Burnout today I found out that I was only at 90% on the comparison?!
Anyway, had a bit of a sneaky look inside, and there's a list of the trophies that will be added in the Party mode when it gets released
Bronze:
Every Player Succeeds in a Party Round
Awarded when every player successfully completes a Party Round
Complete your first Party Round
Awarded when you complete the 1st Round of your 1st Party.
Every player take a photo for a Party
Awarded when every player in a Party takes a photo of themselves. Requires a USB camera to be connected.
Silver:
Every player succeeds in every Party Game
Awarded upon completing a Party in which every player successfully completes every Game of every Round.
Complete a Small Party
Awarded when 2-4 players have completed a party.
Complete a Big Party
Awarded when 6-7 players have completed a party.
Complete a Massive Party
Awarded when 8 players have completed a party.
So there we have it

Dunno how people are going to react with regards to another one that requires a camera, but at least this one won't be needed for the platinum