[Customer]

X. Elite could earn more SP than all other ranks? Maybe 20% more or something?
X.Elite only sub-forum, I know there's already one for Elite users but I think it may be cool to have one for only the most prestigious users.
Ability to change userbar colour as well as username colour?
Ability to add a coloured shadow of your choice to your username colour? Maybe some sort of panel you go to so you can change your colour whenever you want? Maybe even alternatively the ability to add your own CSS to your username colour so you can do cool shit like rainbow name (though I'm not sure if that would look ridiculous)?
X.Elite get access to new multicolours before everyone else? Like, if there's a new multi-coloured theme coming out, the X.Elite members get to try it a few days before everyone else or maybe even whilst it's in development?
Slightly reduced prices in the SP shop?

There's probably a few more but I'm struggling to think at the moment.

These are really nice ideas.