This is an interesting topic. We are realistic that many enter the lifestyle seeking their "fantasy" experience, which includes the "looks" they like in guest stars. We probably started out that way as well.
After much experience, we've learned that plain packages can hide amazing physical, emotional, and erotic delights. Most of the swinger "hot couples" have not been very nice or kind people. Quite the opposite is the case. We both want to like the people with whom we play. It makes the play so much hotter in our minds.
Not to get too philosophical, but in the lifestyle there are groups and individuals for every desire, proclivity, and kinky interest. So, most should fit in regardless of attractiveness.
With all this said, my wife has her preferred guy or gal looks, and I'm attracted to a type, but not exclusively.