Minecraft Loot Bags Mod (old spawner)?

I've been playing Minecraft with some friends for a few days now and we all have the loot bag mod on it. Now my question: Sometimes you get an empty Spawner, called: old spawner. However, no one knows what to bring to conjure except pigs and the Internet is synonymous not explicit about it. I would like to know if you can configure the Spawner yourself, so decide for yourself what spawns from it.

That's fine