You don't see interracial couples on romance novels, either, but there's no rule saying "no interracial couples."

I think you can trust people to understand what you're going for when you say you want a romance cover, without actually having to ban same-sex couples. I know it's not my contest, and I'm not trying to change the rules. I'm just pointing out it's easy to avoid stirring up reactions like Fox's. I mean, what's the worst that could happen if you didn't have a "no gay couples" rule? One or two people might submit same-sex images, and they wouldn't win.