Very well done site Mel. I think it has exactly what it takes to help those new to the hobby and provide the information to get others interested in the hobby. A site like that would have helped me when I was new I think.
Regarding the international one sheet section, I think the poster you have listed for Godfather is actually the UK one sheet (someone please correct me if I am wrong here). It is a subtle distinction, and one that you may be aware of already; but, its the only one of its kind on the page. If you did indeed include it in that category on purpose, then certainly the UK one sheets for The Wicker Man and The Deer Hunter belong there too. Also, three additional worthy international one sheets for the section are Once Upon a Time in America, Das Boot, and Crouching Tiger, Hidden Dragon. I feel like the three of these are all superior to their domestic counterparts.
And finally, a couple of suggestions for additional showcases (and you may be planning these already), are ones for advance/teaser and character posters. Like internationals, they are often very different from the standard one sheet in terms of art. Also, for one close to our hearts, a section for indie and art house posters.
Perhaps, to help you get all of this done, you could add a "contribute" page where interested parties could send you pictures of posters that they feel are deserving for an area of the site. Of course, you would serve as the final judge as to whether the image is added or not. But, lets face it, there are lots of posters out there. Even with the decent sized community of collectors here constantly scouring all corners of the internet and elsewhere, members still often come up with amazing posters that no one has ever seen. I think contributions would be a logical step in the development and growth of the site (if in fact your intent is for it to continue growing).