Blue Rathalos
Get a White Crown for Rathalos in trial mode.

Offline Lao
To unlock Lao offline, you must complete every offline quest including the
hidden ones, unlock the 3 offline color variant wyverns and complete every
trial quest.
When you complete all of those conditions, Lao's quest will appear in the
"Urgent" bracket of the offline quests.
Pink Rathian
Get a White Crown for Rathian in trial mode.
White Monoblos:
Get a White Crown for Monoblos in trial mode.

Additional gallery pictures
Start the game with a saved game file after being online in Monster
Hunter to unlock a fourth gallery page.

PS2 Cheats for Monster Hunter G

Monster Hunter G cheat codes

Monster Hunter G cheats