I, for example, am very turned on by contrasts. So noticeable height differences, size differences (individual body parts or the whole package), skin tone, shapes, etc.
I kinda wish my wife (who’s very pale) were bi because I would love to see her have sex with a dark skinned woman that’s a similar height and weight as her, or a short, petite woman (she’s also tall for a woman).
For me it’s having a very distinct feature of some sort. I don’t know why, but if she is very short or tall, or has a prosthetic limb or weirdly shaped boobs, or a nose like a racing yacht’s keel, it just really does something for me. Like otherwise I generally find most of the same features as many people do attractive, but add that standout trait and whoah, be still, my heart.