I love all the posters, but I have one minor critique with the Gryffindor one. Now while there are many loyal Gryffindors out there, I don't think it's a trait that really signifies who they are. It's definitely a trait that you see in Hufflepuffs, which you also had on their poster. Of course it's your poster for the houses, and you can do what you like (obviously since you did it), but just one small critique (is it even a critique? I don't know).