[2020] What is the biggest storage currenly? Wikis are outdated

Metal Wardrobe is the largest storage official item storage.

EDIT: Also, the wiki is up-to-date on this too. https://unturned.fandom.com/wiki/Category:Item_Storage

EDIT 2: The locker was not removed from the game.

There is no official item called the "Safe". It sounds like you're playing with modded content. You can check your mod list from in-game (Workshop menus) or directly from your Steam Workshop subscription page.

Note that curated content (such as Elver) is not official content. Curated maps may add their own custom content exclusive to that map, and may rebalance or remove official content.