Actually, this is accurate, if it was taken during the movie. The fin Hiccup receives after he loses his foot is red and has a white skull, while the one before is brown because of the leather. The one in the picture is brown, so the tail fin is actually correct. Sorry about correcting you!
But moving on, the picture is very nice. The only thing that jumps out at me as wrong is the length of the tail. The tail is way too long. Other than that, this picture is great. You did a very good job on Hiccup and capturing his emotions. The light is also well done. Congratulations on an amazing picture!