As you said, sitting northeast to southwest, according to the arrival of the eighth day of the eighth lunar month, the northeast is the positive side and the southwest is the zero side, which should be a good auspicious direction.
But feng shui depends on the overall situation of the house, including the surrounding environment of the house, the sitting direction of the house, the internal spacing and decoration of the house, the likes and dislikes of the owner of the house and so on. You can't break the good or bad of Feng Shui with a single condition, otherwise Feng Shui will be so difficult to learn.
By the same token, it is impossible to put a decoration on it, which can turn Feng Shui into a kind of good luck or increase it.