[Cairenn]

Okay, that is more than likely a "Compilation", but I am not sure whose it is. I can however identify at least some of the individual addons within it, and I'm sure there are others that will either know which compilation it is, or can help fill in on mod names. Just from looking at the screenshot, I can see:

The 1/2 rings on either side of the person are DHud
CTRaid
Decursive
The hotbuttons in varying locations on the screen could be one of many. Possibilities include, but are not limited to: FlexBar, BibMod, Nurfed Action Bars
The combat chat looks like HitsMode
The bottom most bar is one of any number of possiblities, including, but not limited to: Telo's InfoBar, TitanPanel, BossPanel, BhaldieInfoBar

The area of black at the top and bottom is accomplished through the /viewport command, part of the default Blizz UI. CTMod has a CT_Viewport that makes tweaking it easier.

Looks like Atlas is included

I'm not sure which Unit Bars are used.

I know there is much more there, but I'm not 100% on some of it, so I'd rather not steer you wrong. Hopefully others can help identify more &/or recognize the compilation (if it is in fact one).

Do you have a link to where you found the screenshot? Was it in a thread somewhere? On a site? Where/how did you find the screenshot?