Some of these things are mentioned in other replies but here are the main things I would love to see;
1. More non-slutty clothes options. Being the seductive girl next door can be fun.
2. Ability to take layers of clothes off as things progress. It would be nice to go from street clothes to my bra to nothing.
3. expanded profile option for those that might want to share more about their background, or read about others, and maybe share pictures as well. Having a sense of someone's background and personality adds a real important dimension. I like to be able to share a photo of myself from time to time, gives my partner something extra to the experience.
4. More options for meeting others naturally as you would at a party.
5. A little more ability to customize avatars to look as close to one's real self as we would like. Particularly (for me anyway) around face details, hair, and breasts/nipples.