I requested a plain clothes domination scene with Mistress Kang, who wore jeans and a tank top. Mistress Tran was a latter addition to the session, and didn't wear them. I just assume that she hadn't been told, which was no big deal. In any case, it was hot. Word of warning though. Jeans smothering is more likely to leave bruises on the face.
I've also done a bunch of sessions where the clothing was more business attire. Pencil Skirt, Blouse, and pumps. Probably my favorite outfit for sessions, really.