Attention! Friday I am going to host a Halo 4 moded custom game lobby message (KChief99) me if you want you join. I got the mods from iHalo4Follower channel, he did 1 or 2 videos about them and also tells you the maker of the mods file share.
I am not sure about the modded content, but I'm sure it is fine to advertise here, it is pretty laid back and even 343i doesn't really care about the mods.