Deemaxm, he's using at least 8 separate kgPanels (or litePanels) in that UI, and I'd bet probably 10.
7 of the visible, and 8 of what I expect the final number us, are to create the gradient border lines (via the method I posted on WoWInterface and yurano linked above ;-)).
The other 1 visible panel (and 1 that I expect matches it on the other side, but isn't visible in his first pic) create the actual background panels - one on each side.
Here's the rough list of panels
4 panels used for vertical lines (2 for each line - one to create the gradient to the top, one to gradient towards the bottom).
2 panels used for the upper horizontal line (one fading left, one fading right).
1 panel used for the lower line underneath his chat (since it fades only to one side).
1 panel used to create the gradient background for his chat (fades only to one side).
The 2 panels I don't see in his UI - well, on looking at other pics, may not be there, actually. He places Skada/Recount in that location, and doesn't seem to have the gradient background or the bottom gradient line on that side. However, they'd be mirror images of the last 2 panels I listed above, if one used them.
@yurano, thanks for linking the post on WoWInterface - I didn't even remember writing that one, honestly!