Not promoting sex, violence, drugs or drug paraphernalia, there for I saw - not inappropriate. Other wise, the school will let you know if they don't like it. It's definitely different for a first grader - there for very cool ~ but hardly what I'd call "inappropriate"
Sounds like he's a normal boy to me. (Of course, I don't have much experience with boys ) It's really your call as the parent if you feel comfortable with him having it. Hope he has a great year in 1st grade. I can't believe a year has passed already, I remember when he started kindergarten. He's the same age as my youngest dd.