A lot of Icons seem to missing with this theme. For instance the icon for “icons” in the menu of the systemsettigngs5. Is this expected or as intended?
I also want to report/remark/warn about libqt5-qtct. This is apparently a library that is supposed to interact with some config tool (that I apparently do not know). In any case: It caused yast2 to segfault on startup. Is this known?
Cheers
Well, missing icons are definitely not intended… 
If an icon is missing, the standard one should be displayed.
Try to delete the icon cache ~/.cache/icon-cache.kcache and logout/login.
As you mention libqt5-qtct, do you have that installed?
That overrides/disables KDE’s platform plugin, and can cause exactly issues like missing icons or the wrong style used.
See also 920792 – KDE 5 Plasma icons are missing after upgrade
I also want to report/remark/warn about libqt5-qtct. This is apparently a library that is supposed to interact with some config tool (that I apparently do not know). In any case: It caused yast2 to segfault on startup. Is this known?
I tried to install it here (on 13.2) now as a test, and YaST still starts fine.
But as it is a Qt platform plugin it needs to be built against exactly the same version libqt5 version as you have installed (IOW, it has to come from the same repo). If you mix versions, crashes are very likely.
And yes, libqt5-qtct is there to make Qt5 applications use the settings configured in qt5ct (a configuration tool included in the libqt5-qtct package).
But again, you shouldn’t have it installed at all when using Plasma5 or you will experience problems.
Inside Plasma5, Qt5 applications use Plasma5’s settings anyway.