If I were to go in detail, I would say every town could have shop or NPC, where Players could go and gamble for or purchase stuff that would add to character customization, such as Light/Visual Effects on Weapons, Exotic Dyes, Custom Aura Designs (maybe Pets?) etc. It can add greatly to the current customization system of Dyes and Banners. There can be a mini dungeon like the brawling area, where players may be able test out their customization before finalizing it.
Of course, nothing that can be exploited or even remotely breaks gameplay.
Also, How I wish we had more gear slots for the followers! They have a right to be dressed as good as the Nephalem they follow! There don't have to be too many 'Active' gear slots, but just for eye candy.