Yes the GTK-Qt Theme engine doesn't change the icons.
To add a new icon theme, you can try installing one you like from http://www.gnome-look.org/
and manually editing the $HOME/.gtkrc-2.0-kde file generated by the GTK-Qt Theme engine, adding a line like :
gtk-icon-theme-name = "Icons theme name"
Alternatively you can try :
1) to uninstall the GTK-Qt Theme engine, along with the ~/.gtkrc-2.0-kde and ~/.kde/env/gtk-qt-engine.rc.sh files generated by it
2) to use an harmonized qt and gtk2 theme like the QtCurve,
look the kde-look.org
site for more infos.
But I don't know if it changes the gtk2 icons.
If it doesn't, you can try the first method given above, with the ~/.gtkrc-2.0 file.
Don't forget to logout/login to have the changes enabled.
I don't think you will get exactly the same look though.
Try different things and stay with the one you prefer.