I couldn't think of ideas for every world, but I have some:
1. Greek Islands- Jet Set expansion pack- join the crème de la crème by buying and investing in various properties. Comes with features like: owning and running hotels, resorts, villas, and a possibility to buy additional homes for your sims. Invest in gyms, museums and other public properties and collect weekly earnings. New feature- paying weekly taxes. New life state: genie- you get three wishes, but careful what you wish for!
2. Italian Vineyard- Gourmet Farm game pack- comes with an overhaul of the already-in-game grapes (introducing new cultivars). Find new grape cultivars and graft them together. Buy a vineyard (new lot type) and start a grape juice (wine) business: employ workers and sommeliers and work together to promote and sell your products. Olives and olive trees also come in this pack. Grow olives and produce olive oil. The higher your gardening skill, the higher will be the quality of your olive oil.
3. Spanish City- Dream Romance- expansion pack- complete overhaul of the attraction system- added zodiac signs, digital dating and more specific types of relationships. Sims now have more romantic interactions like: slow dancing, cuddling, neck kisses...Comes with new wedding decorations and many new flowers to grow.
4. Scotish Higlands- Enchanted Forest game pack- Deep in the woods, in the ruins of medieval castles, the small and peaceful community of fairies found their home. Become a fairy and master the powers that Mother Nature gave you.
Fairy powers: special relationship with plants, they easily find even the rarest items in any collection, can influence other sims through new romantic and friendly interactions. Their handiness skill grows faster. They age slower, but their social and fun needs decay faster. They're sensitive so the sad moodlets always last longer.
Rookie fairies have to earn their wings (butterfly shaped), while powerful fairies teleport with pixie dust.
New collection: new butterfly species and mushrooms (fairies find them more easily). Some mushrooms can be sold at a very high price, while others have interesting effects.
5. Swiss Mountain Town- Classical Art- expansion pack- new lot type-theater, new careers: theater performer: after level 3 you pick one of the 3 branches: ballet dancer, opera singer, puppeteer
2nd career: member of the orchestra, branches: principal and conductor
New skills: opera singing and ventriloquism. New gameplay object: dollmaker: a working station for making your own puppets and dolls.
Evil sims can make haunted dolls. and give them to others, or place them on someone else's property. As long as the doll is on the property or inventory, the household members will have tense moodlet.
New instruments: trumpet and harp.