Ooh! That's a good question and not something I had considered! There is currently no "Tier 4" level to upgrade something to, so I could see maybe it becomes a "buy-one-get-free" sale (two items at +1 Tier for no extra cost), maybe you get an extra tag on that item, maybe it can count as two Brands (like how the Looks the Watchers can drop work). I'd pick something that seems fun and rewarding and that makes that Look feel particularly special!