A variety of body types and races would be nice, there are a large number of model height tanned Caucasian brunettes in the Daz(assming your using Daz) world, a few petite girls, some with a more generous body type, not fat just curvy beyond the boobs and ass, think Siri sort of build.
As for fetishes, anal is a firm favourite for many, feet is quite common though i personally don't get it. A good variety of moods and positions, authors often get stuck on catering to just one style and simply tailoring it to the surrounding, this isn't realistic or fun, just because girl X is exhibitionist of the game doesn't mean that all her scenes have to be in the open, the same goes for any character, just because you want them to have a defined personality doesn't mean they don't enjoy multiple roles or fetishes, just because she's into hard S&M doesn't mean she needs to be tied, bound and gagged in every scene.
I'd also recommend you be careful around any fetishes that will disconnect you from the core player, stuff like scat and watersports or male-male can be a reason people simply won't pic up your game, same for bestiality it doesn't mater if it's only optional content people will see the tag and just go "nope not for me".