Icons in the menu do not change when the theme is changed. This is true even if the theme has an icon of the correct name. The cause of this is that in /usr/share/applications/net-xmtr.desktop the Icon= line has the absolute path to the icon instead of just the icon name. Icon=/usr/share/pixmaps/mtr_icon.xpm When it should have: Icon=mtr_icon.xpm Or even better, it should be a .png.
Fixed in mtr-0.54-5 and later. Read ya, Phil