Oh do I have an ever long list. Let's break it up into categories. Here goes:
Jewellery and accessories: string of pearls, long and short; thick gold chain especially a really tacky-looking one, befitting of a gangster - think Mafia; :D more large, dangly formal earrings in a decent colour selection, I think my female sims mostly wear the same few formal earrings; single gold bangle (not a cuff that hugs your wrist, the kind that hangs off a bit); charm bracelet; pinky rings and rings for the index finger that aren't the creepy eye thing; white colour for the existing leather cuffs; more armband jewellery; anklets, facial piercings and ear cuffs.
As for location of jewellery, I would like the ability to place each piece on either hand. Also, I would like to be able to place an armband and bracelet on the same arm. On the other side of the coin, I would like to be able to add earrings to either one ear only or both ears, of my own choosing, maybe include a setting to auto-place on both ears and you can turn it off to manually place on left or right? Kind of like how you can turn off auto-place counters in build mode and choose the one you want. Come to think of it, you could do it with gloves too, you know, have that whole Michael Jackson thing going on? Speaking of which:
Fingerless gloves. I need them. They're a good choice for several styles.
Onto shoes. Thigh high boots, both heeled and flat and they need to be skin tight. Closed-toe wedge sandals/espadrilles.
Swimwear: sarong and beachwear beach pack, please? o:) , more swimsuits - the bikinis that came in the spa pack were great.
Clothes: polonecks turtlenecks with half sleeves, trench coats, both with full sleeves and pushed-back sleeves, leather gilet, longsleeve top under t-shirt for females - why not make a system like leggings where you can layer long-sleeved under layers with a regular top, the way you can put leggings under shorts and skirts?
Hair: more male hairstyles, the current base game selection is dismal. Trendier styles that are a little longer, but not long (around bottom of ear length?) with tendrils falling forward, very long hair and more long curly styles to complement the ones in cats and dogs, ability to add ombre to any (or most compatible) hairstyles, but also choose the colour I want to ombre with.
Finally, not an item per se, but an option to filter hairstyles by whether they have a fringe or not. I'd be happy and grateful to see any of this. I choose the packs I buy based on whether I'll enjoy the build-mode and CAS items available (if I'm not interested in the gameplay itself). As you can see, I really do enjoy customization.
