Backpack Quark Mod is a pretty backpack mod for Minecraft. It adds a variety of backpacks to the game, and is heavily inspired by the forge mod Quark Oddities. It adds a lot of features, created around what the author likes to call “Player-Focused Design”.
You can customize these backpacks in various ways, such as color, size, and even the number of slots. You can also use different upgrade filters, which adds special abilities to each one. The backpacks also save the contents upon death, and are impervious to lava and explosions when placed.
The config is detailed, with lots of options to tweak the mod just the way you want it. The backpacks are also compatible with lots of other mods, including Curios, Just Enough Items, Botania, and more!
The mod is a dependency of Baubles, which adds an equippable backpack into the body slot. This is required on both the client and server. It additionally requires Sophisticated Core and AutoRegLib. The author has a link to all of those on the official website.