Driving me nuts.

Can someone help with info on creating new sprites? Take any G3 character. I'm trying to scale/size newly created assets(face, hair, etc.) in Illustrator to match the scale/size of a G3 character's assets. Is there any information as to what size each of these assets need to be before saving, then importing to CTA3? 

Thanks.

For first stage elements (character body parts, props) I use 1px = 1mm ratio.
Background objects can be smaller (1px = 4-5 mm), far background (mountains, clouds) even smaller, depending on a scene.
For extreme face close ups you might want a bigger ratio, but I would make separate models for that.