The only time creatures make different noises (like what you hear when you click on them, when they get hurt, the new 'call for mate' ability etc.) is dependent on if they are a baby or an adult. You can have two extremely different looking creatures and they will sound exactly the same.
This feature wouldn't be meant to affect gameplay, it would just be a nice little detail. For instance, it would make sense for a big-bodied creature to have a 'deeper' voice than a normal-bodied creature just because of their size difference. The easiest way to implement this would be to just have it based off of the body types since that could only change the pitch of the creature's voice. Having different sounds for different head types would be neat too but I could see it being more work. It would be funny if spit/derp snouts had a silly voice to match their face, or if beaks sounded more bird-like and purr snouts made more meow-like sounds.
