I know, right? It's a cliche for a reason. In a world where you're one of a handful of survivors in a sea of grey shambling flesh (talk about special snowflakes!), there's a certain appeal to mowing down the inane, mindless hordes of consumers like you always fantasize doing on the rare occasions you're forced to go inside of a mall. It's a beautiful thing, and it even does a couple of things for a module design that I think are really nifty.
1) It lets you confine the area very naturally. Malls are built like ye olde castle, in that you're designed to stay in. It's absolutely intentional- they're supposed to be nearly self sufficient, easy to get in, and difficult to get out. For all of the spacious courtyards and high ceilings, there are naturally a tiny number of semi-hidden, chokepoint-styled exits. When the living dead are all around you, chokepoints are a horrible thing, meaning that once you get in a mall, you're going to need another way out. This very naturally creates drama, because
2) For all of the junk inside of a mall, very little of it is useful in guaranteeing your survival. This means that your players aren't finding rocket launchers or chainsaws (well, maybe chainsaws, but there's not really any gas to power them), which would ruin the feeling of "holy shit, zombie apocalypse." More pertinently, the players aren't going to find much in the way of food or water, except in the Food Court, and the great majority of that is going to spoil very, very quickly and probably be entirely uncooked. Mall food is pretty unpalatable even when cooked fresh, and a couple of days with no power and no new shipments of food is going to leave a horrible place.
3) A mall is a place you visit, not a place you stay. This ties into 2, but in a totally different way. In daily life, you don't stay because you have a home to go to, the crowds are tiring, and the security guards will yell at you when you try to sleep there anyways. In a zombie apocalypse, you can't stay because there's nothing to eat, there's almost no real defense, and there are a hell of a lot of zombies around already, between the people that died there, the other people that thought it'd be a good idea to hide there, and the zombies that wander inside periodically and can't get out again.
4) It ties into the Dawn of the Dead-styled "zombies as consumerist allegory." The less said about that, the better, as far as I'm concerned. I'm not a philosophy blog and I'm certain you expect only those philosophies here which pertain to gaming.
5) It makes sense to get caught there. It almost feels like you're stuck there on a normal day, so getting caught there when everything is zombies? Totally plausible. Furthermore, it's very diverse. Pretty much anybody can be at a mall, meaning that characters can be literally anybody- a vacationing family man, a down on his luck homeless man, a security guard, a trucker just there on a pickup, a UPS guy, anybody.
All of these things are pretty easy to get across, I think, although in a one-page design I'm a bit more brief.
Watch this space- it's on its way soon.