I was uncertain how I wanted to represent the guards. Ultimately, what swayed my choice was the simple fact that I wanted an overhead wide shot of an isolated Cinderella Tedd. The mouse-hunting kitty claws of the guards needed to take the form of obvious weapons that would stand out from that angle, and I felt spears were the best option.
I considered how they would logically be dressed, but given the era of clothes were a bit all over the place anyway, I decided the main thing I was worried about was distinguishing them from butlers. Any sort of suit was out, somewhat light armor with helmets were in.
Granted, few things are more terrifying than an old butler with a spear. He might seem gentle and polite, certainly, but I can't imagine an old butler with a spear, or any other weapon, really, who wouldn't know how to use it with deadly efficiency. Fiction has taught me that this is just one of those things one should expect of an experienced butler.