There are hundreds of buffy the vampire slayer and angel the series icons available for your personal use. Many of these icons even match with the wallpaper selections.
Icons are made with windowsOS. I'm sorry if you have a mac and can't use these icons. I'd be happy to have someone convert them, if I get any volunteers.
Simply download and unzip to the folder of your choice then use your icon utility like ActivIcons
(freeware) to change the icons of any shortcut you like.
Note: Any suggested program is to be used at your own risk. Twilight will not be held responsible for problems caused by said programs.