idea for something to post on garrysmod.org

Ive been really wanting to make something to post on garrysmod.org, and I want to do a save file. so far I think I want to make a save about how you are on a zombie infested island, and you have to stop the zombies by hacking a keypad that is on the island. I am just trying to find out a story for the save. Ill have to think of something, though.