(Changed my original suggestion, after rereading the guidelines for what was being asked for. You want building ideas? I got em!)
It kinda bugs me that there are "bikini top"s but no "bikini bottom"s, so seeing those added would be nice. I second the person earlier who suggest adding in some randomly generated names for stores/towns. It would be a small addition that would add a lot more character to the world.
Notes scattered about the place that give a civilian perspective on the the cataclysm would be cool. They would serve a similar sort of purpose as the Research logs founds in Labs, but either have misinformation, random non-important notes, or funny/strange comments. Maybe occasionally have useful tips for new players (ex: "One of those things broke into my makeshift shelter today. It is a good thing I smashed out my neighbors window and made a crude spear using the string, curtain rod, and a sharpened rock earlier, or it might have gotten me!", or "Got so desperate for water today that I actually drank out of a toilet. Now I can't stop puking. Maybe I should have tried boiling it or something first.") I know that sort of detracts a bit from the whole rogue-like vibe of killing new players because they don't know any better, but learning from the mistakes of others is just as valid and less frustrating than being killed because of a mechanic you could only know about by using the wiki. or by accidentally discovering. Still, because it IS a rogue-like, and failure is part of the fun, I'd say these "tips" should be really simple stuff, and not always actually correct. That ought to keep things interesting.
Suggestions for new buildings/locations (with suggestions for what could be found at them):
Post Office buildings, and mail-carrier z's which spawn there (perhaps have them drop fliers, magazines, and packages that can be dismantled for random clothes/electronics). As is, random z's are wearing bits and pieces of a postman's uniform, but there is no mail, and there are no post-offices to justify it.
Campsites in forests, with the corpses of backpackers, granola, canteens, tents, and other camping supplies. A cursory look at any sporting goods store shows that backpacking and camping were alive and well in the setting, so it is a little weird that there aren't actually any campsites.
Carnival Grounds. They would be a great source of metal frames, be an interesting location to have a stand-off with z's, and maybe have lots of junk-food scattered around. It gives an excuse to add more junk food to the game (funnel cakes, cotton candy), and another location to add in the rarely-seen food carts. Also zombie clowns are terrifying. Perhaps they could drop clown suits, clown shoes (high encumbrance, make noise when you walk), and bicycle horns. The parking lot outside the grounds might be a good place to find working cars, or even a bus or two (for the carnies).
Beauty Salons in the towns, where you can find some housecoats, spray cans (for hairspray I guess), beauty magazines and the like. You could probably dismantle the tanning beds for heating elements. Chemicals and scissors could probably be found here too, as well as whatever items were left by panicked patrons who fled when the cataclysm happened.
Community Theater Houses. They would have tons of seats, be a large concrete building with few entrances/exits and no windows (so not a bad place to turn into a base), and backstage you could have lots of floodlights, prop weapons, and exotic costumes. It would give an excuse to add in clothing that otherwise wouldn't make sense a "20-minutes into the Future" setting.
Jewelry Stores. Pretty self explanatory, and give those survivors so inclined a way to bling themselves out. You might occasionally find ridiculously extravagant jewelry in there. (Giant iced-out dollar sign necklaces, crowns, tiaras, pretty much anything Flavor-Flav would wear). Also would be a reliable place to pick up a watch.
Gentleman's Clubs. Not in town, of course, and I dunno if these sorts of places are all that prevalent up North, but down here in the Southern states you can pretty well count on passing at least one strip club along the road if you go on a long road-trip. These would be found a bit outside of towns (like gas stations, perhaps even next to gas stations), and would be good sources of booze. In the back rooms you might find various undergarments, costumes, drugs, and in the managers office maybe some guns and money piles.
Zoos. It would give an excuse to add in some more exotic animals, and be a really interesting location to explore/use as a base. Though if zoos make it in, I would suggest having them be an optional thing, to accommodate differing ideas of the time-frame of how long ago the cataclysm happened.
I feel like any and all of these would add more variety, and therefore entertainment, to characters who have made it past the initial couple of days of frantic looting and have begun to actually explore the world.