Bridalwear/Tux Shop
Wedding dresses/outfits and lingerie for brides, and suits/tuxes for the guys. I can probably add sexy sleepwear for the guys too with that silky robe coming to BG. I might also split this into several shops on one lot with a dress shop, suit shop and a bakery for the cake. I don't usually have bridesmaids outfits here due to only having 5 outfit slots per category/age/gender shared by all mannequins on the lot.
Maternity/Nursery Store
All the bassinets, toddler beds, baby/toddler décor, toddler toys, highchairs, potties, nightlights etc. I'll have mannequins wearing outfits suitable as maternity wear, for all genders. I believe you can adjust the mannequin bodies to look pregnant too so you can see what the outfits look like with a belly.
Toy Shop
Toddler and kids toys and books, activities and decorations plus the kids collectibles like MySims, Simmies, Meduso plushies and VoidCritter cards and device. I might also sell fun items that adults can use too, such as game tables, game consoles, foosball table, darts etc. Also, any associated merch like game posters, VoidCritter pouffes, MySims decals etc.
Kitchen & Bathroom
Counters, islands, cabinetry, bar stools, (upgraded) plumbing objects and (upgraded) kitchen appliances. I'll also add shelves and wall displays full of associated clutter/accents like towels, robes, fruit bowls, knife racks, pans etc.
Furniture Stores
A modern, IKEA type layout of contemporary living/dining/bedroom/study furnishings and associated décor like modern art, rugs, potted plants, clocks and sculptures. Maybe some of the nicer clutter things too. Also an antique store with a more cluttered layout of the heavier wood/more antique styles like Queen Anne and Storybook and décor items that look older or more classically styled and genuine artefacts.
Pet Shop
Pet furniture, toys and treats. I wish we had pet mannequins to sell collars and clothes here too. You can also sell aquariums, rodent cages and the GF pond object. Maybe sell collectible frogs, insects and living aliens too as small pets. Chicken coops and animal sheds are an option too, for more rural worlds. I don't think you can sell the animals themselves, but I haven't tried it.
Music Shop
Stereos, amps, instruments, mixing deck, DJ booths, dance floors, microphones, karaoke machines, music skill books. Music related décor and merch such as CD stack, band posters, band tees and jeans outfits on mannequins etc.
Craft Shop
Easels, knitting & cross-stitch bags/boxes, cross-stitch hoops, llama wool, yarn balls (pet toy), lumps of clay, soy/bee/wraith wax, kids craft tables, pumpkin carving bench and workbench. Career unlockable CAS items like the paint-spattered tank top, artist's smock and apron via mannequins.
Beach Shop
Swimwear and dive gear on mannequins. Grass skirt outfits. Floaties, portable lounger (the BG one), coolers, soccer ball, grills/BBQs, fishing traps, local mounted fish, shell/treasure collections, diving prints, diving gear furniture/debug items, Aqua Zips and island canoes.
Pharmacy/Alchemist/Herbalist
Completed potions, herbal remedies, mixology potions, medicine, debug sunscreen and massage oils, clutter toiletries and supplements etc. Also herbalism and alchemy ingredients (produce, bugs, crystals etc).
Occult Shop
Soul scraps, sacred candles, candles, crystals, séance tables, crystal balls, paranormal artefacts and décor, creepy doll (or it's safe lookalike), creepy paintings, mystical jungle artefacts, cauldrons, familiar orbs, broomsticks, book stands, vampire lore books and spellcaster tomes, vampire cure and other vampire drinks, spellcaster potions. Also have a séance table not set for sale so the owner and visitors can perform séances.