Doesn't really matter, but I like Irish and British accents in both genders. An accent similar to my own (Coloradoan, so a generic and non-region specific American) is also good, and an intellect with a Southern accent isn't bad either.
I prefer a caucasian woman, but i mostly care about her interests. I won't complain if i see a girl who likes heavy metal and drawing like i do. And i also care about character, an open-minded girl is a plus to me. But if it is about appearance i am not that picky.
For men I can't really say.. just any European nationality. Many Dutch, Finnish, and Icelandic women are extremely attractive, but that's more of an admiration than an attraction. My boyfriend's Austrian, and I'm American.. but I think there are attractive people in every race and nationality, clearly. I just like mah white men.