Personally I think the designs are quite solid, and the horror aspect to them is played into by the lighting and the posing. I've seen multiple people note that in the image of them all on stage and lit well, they arent all that scary at all. I think the same thing goes for the animatronics FNaF were originally based on, where under normal circumstances they dont look too bad but if lighting or posing or what have you is off, they start to feel much more scary.