Lucy has made high quality versions of the HPosters available for you to download or print or whatever. She has a PayPal button on her site - make use of it if you download one of these!
And by the way, I guess there are spoilers in the last poster. But the rest can be a nice way to get up to speed before seeing Harry Potter and the Deathly Hallows Part II.
Thanks to @webacion for the link,