Here's a picture of the new inventory window:
As you can see you can put anything you could normally wear into the appearance slots.
Here are some other requirements:
1. You must be at least level 20 to use the appearance tab.
2. Hotkeys and macros will put gear in either your equipment or appearance slot, which ever tab you looked at last.
3. All gear must be attuned before you wear it now. You can no longer wear unattuned gear.