Yes, anyone can do it.(I use paint shop pro, but any good graphics program will work) But when you put the skin on,it seems to have limitations on the shape of the eyes and nose.If you put a different shaped eye on the skin, it looks weird when you put it on the body.
It's kinda like what would happen if you took the face with slanted eyes off of an oriental, and put it over your face. You may still see what's behind the "mask". I could be wrong, but that's my experience. That's why fullbody skins are limited. The eyes, nose and mouth have to line-up properly, or it looked like 2 superimposed pictures. And funny looking.
Now if someone could change the shape of the features on a full_body htr............................