Everything other than gallery pictures is unlockable via time release. This means time that you are playing the game, NOT time spent in the main menu, character selection screen, in between arcade matches, etc. There are normal ways to unlock these, but time released seems to be the easiest way.

Unlockable	How to Unlock
EX modes	Every hour after 48 hours, an EX character will be released. Starting with Potemkin and then Chipp, going in the same order as Survival mode.
GG Mode	48 hours of gameplay.
GGX Mode	24 hours of gameplay.
Shadow and Gold modes	Every hour after all the EX characters are unlocked or 48 hours, whichever comes last. Press D with Reload colors for Shadow, Slash colors for Gold.
Slash levels	Once all EX, and Shadow/Gold characters are unlocked and you've spent at least 48 hours a Slash level will be unlocked. Press R2 for the #R stage ver.