How would I go about using a creature mesh for a body part? I wanted to create a race based upon certain creature parts, but whenever I remove what I need to from the mesh, and eventually assign it to the race in the CS, the part will be invisible.

EDIT: I'm using NifSkope.

You'll need to either remove the bones & animation from the creature meshes (easy-ish), or weight the skin to the bones as was done with Better Bodies, using a 3D editing program.