My guess is that the wax model that became Mr Ugly was intended to be a regular, symetric mace head, but that the maker simply decided to "do something Fun" instead of giving it a smooth finish.
I can imagine an aprentice or somesuch having a go at a spiked mace, like other example, and, after cursing at not getting the ribbons and spikes symetrical, making a face instead.
Master:"You spent bronze casting THAT!?!"
Aprentice: "But I sold three allready..."

Another point (or lack thereoff) worth noting is that the spikes on Mr Ugly are quite rounded, unlike the ones on Spike. After trying them in hand, my guess is that Spike is made to be a weapon of war, while Mr Ugly could serve as a "walking stick" kind of mace, where sharp spikes would be unpractical, and hitting people without killing them could be a pluss.