For my old Slanneshi WoC list I simply used those ancient metal chaos trolls and went wild with greenstuff, added a boob here or there, some (literal) balls behind those loinclothes, and swapped their fists and weapons for Daemonette claws and pincers. Cheap. Simple. Awesome looking. But Boobworms are also a neat possibility !
@Datalink: Yeah I was thinking about that one, but I'm leaning more towards the Banelegions giant pretty much naked god thinggy that they have. But that one is cheaper! Maybe I'll pick them both up for that 1 time that my only unit champ in the army (or any of my characters) end up becoming a prince.