>>96367548
Since ghouls are a mix of high medieval and some late medieval, burgundian courtly era I think a huge bombard could be cool for them, something like the guns of Orban. Although the question is whether ghouls would be smart enough to operate them, maybe they could have a few engineers captive to work the guns for them, mongol style.
I also had an idea for a ghoul warmachine battering ram, but instead of a finely sculpted head they just found a big wolf or goat beast and put its severed head on a big log. See picrel.