I have a couple of malls, they sell clothes (Moschino, everyday, swimwear), music instruments, bakery goods, pet treats, Christmas decorations, electronics, small gift type objects like vases and future cubes, baby furniture, make-up decor, toys, shoes. I also have some smaller shops that sell flowers, books, jewellery, icecream, wedding dresses, shoes and lingerie, seasonal clothing. I had a knitting supplies store with an area for knitting, but it got demolished. I also have some sims that sell stuff on the sales tables, so not really stores, but they could be. One sells honey, another one sells apples and apple juice, and another one sells relics and emotion berries. I have plans for a photography shop, but I haven't decided yet if it will be a proper shop or just use those picture displays. Anyway, I guess you could make a shop to sell just about anything, though some objects like the small aquariums cannot be set for sale, and sims can't reach objects placed in some glass displays. But if you want to make craftable objects available to other sims who don't craft, shops are a great way to do that. I also use the shops as places where sims can access the different craft machines, so they can either buy or craft items themselves.