Today ArenaNet launched a Hall of Monuments Reward Calculator web page. All you have to do is put in your character's name from the original Guild Wars and the calulator will figure out the rewards that will await you when Guild Wars 2 is released. There's more info on this feature on a FAQ page and more info on the feature can be found on this news posts. You might be able to gain access to things like in-game pets, special weapons and armor pieces and more. You can even let other people see what kinds of rewards you get via social networking pages like Facebook.
Gallery: Guild Wars 2 Screenshots