well, i think the font is a bit too cartoony, go for flat type.
the poses are cool, but you should add some more contrast and maybe a darken the sides of the image to make the viewers attention center on the middle action.
i would also advise you to minimize the text on the poster... and zoom in on the main action (vampire attacking)
of course, you could consider all of the above to be useless blabber by an insane person...