Surprisingly Sagaoz doesn't have the complete save file for a full gallery unlock yet.
Since the save file attached from the Chinese forum is most likely out of date, I'm attaching mine. I know it works if players have all of the DLC installed, those who are missing 3 but have the rest may or may not be able to use the files.
While I'm at it, guide to DLC3 and DLC4.
DLC3:
No new heroines, but players can take on the adventurer's tower and its 100 levels for loot and goblin stats. The stat boost only applies the first time players reach a stage milestone, afterwards it's probably better to just run the later levels unless players are desperate for the new goblin extras.
Registering the game allows players to take on goblin nests managed by other players. I haven't tried this mode, so no idea how it works exactly.
Speaking of goblin extras:
Wolves: These are a boost to regular goblin packs. 50% chance to avoid a physical attack when fielded.
B-grade breeding vessels: These are a boost to hobgoblin packs. 50% chance to avoid a magical attack when fielded.
Note: Using either wolves or breeding vessels stops the alpha from initiating the loot command.
DLC4:
Two non-human heroines. Unlike DLC2, these are not end-game material and are really there to help players in the early stages of the game.
Page: The hobbit/halfling who's good at drawing. I feel a little sorry capturing and turning her into a breeding vessel since she's not the type who opposed the goblins or had a perverse interest in their habitat and ecology. Her stage appears before Erda's.
Boosts magic: Skill is a slightly weaker version of Simona's (0.9x modifier instead of 1.1x)
Drops 女の肉 on death.
Luna: The succubus who's fed up with her usual cuisine tasting awful thanks to goblin-induced stress. She will attack the nest after her appearance is triggered. If there are multiple active heroines, the usual rule applies as to which heroine attacks on day intervals divisible by 7.
Boosts attack: Skill drains 2 mana from target enemy. This is actually useful, especially for paladins and shamans. Instead of the usual combo of mass heal + mass attack, now players need to choose what kind of role they want a unit to play and to use the mana drain skill appropriately. Paladins and Lords can get more heal/mass attack spells in, while shamans will probably want to combine mana drain with the Asterea mass attack spell for serious carnage in prolonged battles.
Drops 貴女の肉 on death.
Ending: Get both Page and Luna lewd. Status of all other heroines is irrelevant. If DLC2 is present and Asterea has been captured, she needs to die before the ending can trigger earlier before turn 90.