So I just thought some Visual Effects would be cool. I thought about custom tabards that you would be able to buy for Honor / PvP Tokens or whatever. It's just when you equip them, you get a visual effect (if it doesn't work you can make the visual on USE).
Here are some ideas:
Shadow Image Visual Aura - 45263
Dark Iron Light Aura. Red - 47760
Strength of Ossirian Aura - 25176
Alextrasza's Gift Visual - 61023
New Shadowform - 55086
Corruption of Time - 60451
Corruption of Time - 60451
Ghost - 8326
Headless Horseman - burning (cosmetic), base - 43184
NOTE: I am not sure about those names and IDs, I can't promise they are the right ones! It's just for example.