I really like the Hellhound idea especially making it open topped and such with a little diorama of action going on.
As for Centaurs I'm not sure for size since I dont own and ratlings for comparison. I do have dwarfs and a couple hobbits form LoTR if scle pics of those would help. And once again if you buy the FW Centaurs I'd love to take the Kriegans off your hands

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BvL