You can use these skins when playing the Deja Vu mission.

Skin	How to unlock
Classic Gray Fox Skin	Recreate each photo in Deja Vu mode on Hard mode, and answer each MGS Trivia question correct.
Classic Snake Skin	Recreate each photo in Deja Vu mode on Normal mode, and answer each MGS Trivia question correct.
Raiden re-skin (White)	Complete Jemais Vu mission on Normal difficulty.
Raiden re-skin (Green)	Complete Jemais Vu mission on Hard difficulty.