I have the same question as the guy who posted it on Debian mailing list (and received no reply):
Since I upgraded to kde 4.6 there are no background image on Superkaramba themes (running through Plasma). Is there a way to tell Superkaramba to use Plasma widget backgrounds?
(source: http://osdir.com/ml/debian-kde/2011-04/msg00071.html)

thanks for your answer

Can you please post a link to one of the affected SuperKaramba themes so that I can try to reproduce accurately?

Any theme without background defined in .theme file.

You can reproduce it by creataing a file with (for example) this content:
karamba x=0 y=0 w=280 h=330 interval=1000 LOCKED=true
defaultfont font="Sans" fontsize=9 color=220,220,220 shadow=0

In KDE 4.5.x, background from Plasma theme was automatically used, when no background image was set (f.e. image x=0 y=0 path="bgr.png")

Well you can try with: http://kde-look.org/content/show.php/Cr ... tent=28165

I can confirm the bug under KDE Trunk - along with another bug (namely - it is impossible to remove that SuperKaramba applet...)

Please file a bug report at bugs.kde.org.

https://bugs.kde.org/show_bug.cgi?id=275383