I know this isn’t an illustration, but an act of graphic design. This is the cover of the essay I’ve made on the Knight Templars, in Spanish for the reenactment group I’m part of: the Orden de los Caballeros de la Cruz (Order of the Knights of the Cross).
It’s a simple layout with the group’s symbol and name on top, and mine on the bottom as the author. The cover illustration was taken from the Chronica Majora by Matthew Paris, this represents the usual image of two Knight Templars sharing a horse (because of their vow of poverty) and the black and whitebanner they carried to battlefield in order to rally their troops.