Mine Trading Cards is a mod about collecting trading cards.
Mobs will occasionally drop Cards Packs, Edition Packs, or packs of a given rarity. These packs contain Common, Uncommon, Rare, Ancient and Legendary cards.
You can also meet various villagers who specialize in selling or trading cards.
Cards are loaded in "editions" (sets or groups) from files separate from the mod. New cards and even new editions can be created by adding new files to the mtc folder.

Installation

Installing the mod works just like any other forge mod—put the .jar file in your mods folder.
Mine Trading Cards has extra files that must be downloaded and installed separately to load the default card sets.

.minecraft
      ---->mtc
            ---->assets
            ---->cards
            ---->editions
            ---->packs (optional—see "Custom Packs" section below)

As of update 3.1, MTC loads content packs from resource packs to save memory
Extract any of the content packs found here or in the discord server's #content-packs channel into that resource pack
There are template resource packs in the mega link
This new structure should look like this:

<resource pack folder or zip>
      ---->assets
            ---->is_mtc
                  ---->mtc
                        ---->assets
                        ---->cards
                        ---->editions
                        ---->packs (optional—see "Custom Packs" section below)

Edition Packs:

Various pack editions are specified in the /editions folder, like so:

{  
    "id": "my_edition",  
    "name": "My Edition Pack",  
    "color": "#55ff00" (optional—see below)  
}

You do not need to specify a "color" field. If you don't, MTC will procedurally generate a color for the pack icon based on the id.

Custom Packs:

You can create custom packs, with amounts of cards based on categories and rarities!
Example:

{
    "id": "test_pack",
    "name": "Test Custom Pack",
    "categories": [
        "Minecraft Mob:2:common",
        "World Item:3:common"
    ],
    "color": "#ff0088"  (optional—see below)
}

Place this .json file into the /mtc/packs/ folder.
You do not need to specify a "color" field. If you don't, MTC will procedurally generate a color for the pack icon based on the id.

This pack would contain two common cards with the "Minecraft Mob" category, and three common cards with the "World Item" category.
All .json files in /mtc/packs will be loaded as custom packs.

Discord Server:

If you want to post a content pack, put a link in the discord server!
https://discord.gg/TWDcAaX
I (Powerthegreat) WILL NOT BE ACTIVE ON DISCORD FOR THE FORESEEABLE FUTURE. Please be respectful of the moderators there.

Forum thread:

https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/2913625-mine-trading-cards-open-source-updated-by
This mod was originally developed by Tradeworld (Minecraft Forums username, AKA nogier (github) or R4p3lay (on curseforge)), then made open source.

Source code for 1.7.10 - https://github.com/Powerthegreat/Mine-Trading-Cards-Source
Source code for 1.12.2 - https://github.com/Powerthegreat/Mine-Trading-Cards-Source-1.12.2