I am not talking about the in-game paragon banners that you get...
There are many cool portraits and avatars in SC2 and WoW, (I have an Aberration portrait from SC2). How come Diablo 3 doesn't have this?
D3 should input a rewards system that correlates with certain achievements, (Reach 100 paragon, complete campaign on inferno.. etc etc).
These rewards would consist of portraits, maybe new skins. (tired of the bearded barb). Maybe new skill animations.
Or you can even take the "skins" idea even further. For example, like armor. ilvl 63 armor on a barb is this blackish red demon like armor, perhaps that can have an alternate armor scheme?