In short: the answer to that question can be found in my previous response. A new item in your wardrobe results in new possible combinations/outfits.
However, I don’t think you can approach the purchase of each piece as an “additional unit” of fashion. If I were to purchase 10 of the same jacket, diminishing MU would hold. However, each piece, in my mind, is significantly differentiated such that it is in it’s own class of goods, unlike consuming the 10th pint of beer. It really comes down to uniqueness.