I think that Irregular Miniatures do packs for cavemen v. mammoths as one alternative, and Victorian explorers v. either mammoths or small dinosaurs for Tusk. There are also a couple of extensions to the Tusk rules for 15mm figures, Tusk 2 and Tusk 3, that give more options.
Tusk in 15mm interests me because MY Miniatures do stuff in 15mm for the Ice Age. On the other hand, 6mm would be easier to paint. Decisions, decisions….