My SO generally hasn't deviated from anyone that is physically similar to me: well-endowed, average height, dark. That's his ideal. All of his exes but the one just before me have had all of those attributes. He's open to all races, and skintones, but he does have a preference with regards to things like curves (a must). As for anything else, they can't be too sensitive, or easily offended, or religious.
He has run into a lot of immature, wishy-washy older AND younger women though, which I know has been disappointing. Out of all of them I've only liked one, and even she ended up going on some rant against poly one day after they had stopped communicating.