The only reason normally shaped rocks seem usual is because that is reality, the way they were Created. We're used to how things actually are, so they seem normal, ordinary, and unintelligently designed, because that's all we know.
sorry but that line of thought is basicly wrong,what about things we create? we can even design objects that look natural (hard thing but possible)
there are objects that look designed but arn't, how can you tell the difference anyway