Media depictions would have it that in some militaries, soldiers traditionally paint icons representing enemies they have killed or materiel they have disabled on the weapons used or vehicles operated in doing so. What terminology is used for these images?
These "glyphs" are called kill markings. I couldn't find a good definition anywhere, but I did find numerous references on Google. The most source worthy is a captioned photo of a 1942 fighter plane.
This post from an aviation forum discusses whether or not "kill markings" were seen on WWI fighter planes.
In my research, I also found some reference to the glyphs as "victory markings," but this usage seems less widespread than "kill markings."