It has been my experience that when it comes to foals heads, it does not work the same way as growth spurt gawkiness as seen in other areas of the body. Most often, a foal will have a pretty head at birth, and as it ages, it develops more and more into the head it will have as an adult. Normally, it gets "less pretty"(or maybe "less extreme" would be a better choice of words) or stays the same, but I have never seen one get ugly(or less than pleasing) and then turn out nice at maturity. BUT, that is only my personal observations.