Visible mods in the screenshots:
Squeenix (minimap)
eePanels2 (unit frame borders, graphics on the top and bottom
Grid
Quartz
Omen
ElkBuffBars
Cooldown Timers 2 (cooldown bars)
BigWigs
Scorchio
Mik's Scrolling Battle Text
RABuffs (shows what buffs people have/are missing, to the right of the action bar)
Bartender3 (with cyCircled VolM)
Pitbull
Notables:
The dots under my player unit frame indicate buffs, which are then filtered out of my ElkBuffBars to reduce the amount of spam on my screen. Left side is Int, Fort, Spirit, Mark. Middle is Food, Flask. Right is Kings, Salv, Wisdom.
The thin blue line under my cast bar is a slightly modified mod called Fudge. You can set it to a spell (Fireball) and it'll change colors based on whether you're in range or not. I modified it to not have a border so I could make it a small thin line. It's blue when I'm in range and red when I'm not.
Omen is displayed during combat, some stats mod is displayed out of combat (Assessment is what I was using until it didn't get updated for 2.4). They've both stripped of any backgrounds and borders so that they fit in with my custom images.
I have two sets of bars for Cooldown Timers 2. In my screenshot only the left set of cooldowns is visible. The right side (above Omen) is short cooldowns (<30 seconds). Short and long cooldowns typically are for different purposes and it's good to be able to distinguish between them easily.
RABuffs is modified to be much smaller and less intrusive. I stripped it of all the custom graphics it uses for its title bar and border. I also edited it so the bars could be much thinner and the font much smaller. I haven't decided on a final position, but with its size it's very easy to fit it places. As a raid leader I need buff information available to me and I prefer the display of RABuffs, but out of the box it is just way to big and clunky to fit in an aesthetically pleasing way.
A recent update of Omen readded the column names (Name, Threat, %). Since that screenshot I have disabled them. I'm very big on disposing of unnecessary labels. I KNOW what the columns are, I don't need a display to show me that. As a result I've gone out of my way to get rid of any unnecessary labels/wording on my UI such as my alteration of RABuffs.
I'm planning to set up the space where Grid is as my place for group raid frames if I'm in a 5 man. I'm big on reusing space whenever possible (similar to Omen and Meters occupying the same spot). I also like making my UI look natural no matter what I'm doing. So even when I'm not in a raid and there's no grid it doesn't look like there's something missing from my UI.
It's taken me a number of weeks of constant tweaking to get my UI to this point where I really like it. It was difficult to make it aesthetically pleasing while also functional. I've never been willing to compromise on functionality and as a result my UI has looked like crap most of my WoW career. As a raid leader and someone who plays multiple classes in raids I need a lot of information available to me at all times. From an aesthetic standpoint, I really prefer things to be symmetrical which is very difficult to do in a WoW UI. Ultimately, after a lot of work I was able to find a balance between functionality, utility, and aesthetics.