My son sometimes gets this look on his face like he thinks his artwork isn't as good as mine. He doesn't realize that I've had decades to get to my level, but more importantly, that his work is just as good relative to his age group AND has the charm of a child's earnestness. Your son's snowman is wonderful just the way it is. Tell him he can trust that this is true because I am just some random internet person who is under no obligation to say things to make him feel better. :)
I fully agree with April. That snowman is one handsome snow creature!
Please, be respectful. We're all friends here. We can disagree with respect.