I'd like to see simplified CSS if that's possible. I've seen it on another site and it's used mainly for post customization in terms of looks, templates, you name it. While it could potentially create some issues, I'd definitely use it if I was decorating, say, a guild page.
If that cannot be implemented, I'd like to see backgrounds for posts. For example:
[background=#000000]Text here[/background]
or
[background=image url here]Text here[/background]
A simple BBCode that would make life a bit more easier is [hr][/hr] for the dividing line (I don't know the proper terminology for this D: ). For roleplays, many people usually write for more than one character in a post, so distinguishing between these by means of a simple divider would help those (even if they write in default font colors).
Other than that, I feel the add media and YouTube BBCode buttons should be combined to just be add media with YouTube as a drop-down option. There should also be an option to hide/remove the BBCode/emotes buttons when writing a post since there are many users who don't need/use said menus. I find them more of a distraction than anything. Along with that suggestion, with the lite forums in place, people may have a hard time loading/viewing BBCode, so an option to disable all BBCode might be advisable.
Edit: I apologize if I seem a bit overly formal or judgmental. I usually don't post in the forums anymore, so I'm not entirely sure how to act.