I think it would be neat if buying some items influenced your champion's look

For example, buying Iceborn Gauntlets on Vi. Sure, it's not necessarily anything I would buy a lot when playing her, but in those niche moments when you do, it would be pretty awesome to have those blue spiky gauntlets.

Other fun combinations could be: or

Just to name a few. Obviously, as with most other decals, this would be something you could toggle off.