The name, Barbarians and Librarians, is fairly self-explanatory, but I will add that out of the canon of rhyme-schemed party themes this is indeed one of my favorites. There are those that will tell you that CEOs and Corporate Hoes, or Golf Pros and Tennis Hoes are best, but in my perspective they are, in fact, lesser themes. Think of the primal capacity of barbarians in all of their raw sexual power, and the converse appeal of the chaste librarian, who has a large IQ, but, secretly, an even larger sexual appetite. Yeah, its kind of like that.
Guys should probably dress as barbarians, if you need an idea of what that might look like, google image search “Conan the Barbarian.” Arnold Schwarzenegger will teach you everything you need to know.
Women can dress as sexy librarians, or if they feel like it, perhaps even barbarians.
Otherwise, drinks and other aspects of the party can pretty much remain the same.
The general beer, liquor shots, or jungle-juice are all good ideas. However, if you really want to commit to the theme, see if you can find Mead. Mead would pretty much solidify the awesomeness of this theme.