This is a way to store your favorite posters for later viewing. Each poster page would have an "add to Favorite Posters" button when you're logged in. There'd be a link on the site called "Favorite Posters", where you could browse the the ones you've selected - in a manner simililar to browsing "new arrivals", and there you can remove any you no longer want to save.
For the database, it'd just be a matter of setting up a new table with feilds of user_ID and poster_ID. The "add to Favorite Posters" just adds a new row, and the "Favorite Posters" page itself pulls all poster_IDs with the matching user_ID. So it'd be pretty easy to set up I think.
Another possible idea off that would be creating a page displaying the most popular posters, the ones with the most poster_ID's in the favorites table. That way the most liked posters get more exposure, aside from the few POTW ones. In order to prevent fraudulent accounts being created for means of self-promoting their posters on this page, you could only count favorites coming from users with a certain number of posts, 200, 500, or whatever.