Faenza Cupertino icon theme, a blue flavor of popular icon theme Faenza has been ported to KDE thanks to TheDeviantMars and the Plasma Desktop just looks amazing. The icon theme seem to blend well with blue KDE theme. Have a look yourself.
The icon pack is as large as 63 MB in size but looking at the screenshot, I think no one can resist and will end up in installing it. Download it from here
[Screenshot from TheDeviantMars]