Have you checked the City-Data stats pages? There are so many places in WA, and it's hard to narrow down from the info you provided. Maybe climate -- which is quite different in western and eastern WA, and even quite different in parts of each -- or population could be a starting point?
Besides climate and population, you might want to consider:
cost and availability of real estate or rentals
groceries, and other shopping
medical facilities
entertainment/activities/sports/internet/cable TV
public transportation
places of worship
degree of isolation during winter months
nearness to city facilities
land, or no land
and whatever else interests you.
