When I try to run lxcc (lxde control center) I get this error message:

Traceback (most recent call last):
  File "/usr/bin/lxcc", line 157, in <module>
    app = Simple()
  File "/usr/bin/lxcc", line 141, in __init__
    pixbuf=it.load_icon('gtk-stop',48,gtk.ICON_LOOKUP_FORCE_SVG)
glib.GError: Icon 'gtk-stop' not present in theme

This is because /etc/gtk-2.0/gtkrc contains:

gtk-icon-theme-name = "Adwaita"
gtk-fallback-icon-theme = "hicolor"

and none of these icon-theme defines the icon gtk-stop.
A solution to fix the problem is to define (as it is done in Leap 42.3):

gtk-fallback-icon-theme = "gnome"

which does define the icon gtk-stop