There is a set of guidelines listed on the HTC skins submission page regarding what is acceptable WRT skins. This includes the following:
We will not accept skins containing the German swastiska. NOTE: If you are making a skin that originally had a German swastiska, just leave the spot blank where the swastiska would have been, or change the swatiska to the Iron Cross. Use your best judgement on this.
I've always taken this to mean kill markings as well as the LW tail marking, but if you want to be sure just PM Skuzzy about it.