Loading custom PK3's into GZDoom Linux?

I know how to load a custom iwad from terminal (gzdoom -iwad Doom2.wad) but how do I add custom wad's and pk3's?
I'd like to play more than just vanilla Doom 2.

-file xxx.pk3

Use the command -file xxxxx.wad or xxxxx.pk3 or whatever. You can load multiple PWADs at once this way, using only one instance of the command, i.e. -file xxxxxx.wad xxxxxx.wad and so forth, but note that later data in the sequence will overwrite earlier data in game. That is, if you load two WADs that both replace map 01, the one that will actually show up while you're running the game will be the second in the sequence above.