It's been a while since I took UI shots. I often get people asking to see my UI, but the last time I took a screenshot to post was of us just starting to attempt Felmyst.. so the shots were slightly dated.
Here's what I use currently (click for larger images):
Solo (no target):
Showing the fact that I have no visible buttons on my UI. Any buttons that I do use are hidden; most of my abilities are bound and only seldomly used items are on invisible bars (see pictures below).
Solo (target, ToT, cast bars):
Secret stuff revealed:
This mostly speaks for itself - all of the hidden elements on my screen. I don't use any bars to play; the hidden button bars in this shot are for things like mounts, tradeskills, food, etc. I have a few oversized empty buttons that I use for gimmicks or quest items. Generally speaking though, there are no buttons on my screen that I use in combat - everything is bound.