Try to think of the county's achievements. Like, for example, maybe your county is famous for art prizes during the summer. Something artsy could be incorporated into the flag. Or maybe they've won musical competitions a bunch of times, so something musical could be incorporated. What defines this county above all others? Is it close to a body of water? Does it have acres of farmland? Pick something easily distinguishable and use that as your base image (it would have to be simplified of course). Also try to use stripes, stars, or some other symbol to represent number related achievements of the county. Obviously the American flag has 13 stripes to represent the original colonies and the 50 stars to represent the current states. Think along these lines and use these symbolic checkmarks in combination with the base image I mentioned above. By then you'll be well on your way.