Stamp design and messaging has changed over the course of the last one hundred years. For most of the nineteenth century, stamp design was simple and rarely changed. New issues were uncommon and Commemoratives unheard of. Design was meant to identify the label quickly as an official government item, a bearer bond so to speak, which indicated a prepaid service of a certain amount. The denomination needed to be clearly indicated (and most countries used color coding to help with denomination recognition- on US stamps the first class (3c) rate was red and the transcontinental rate (10c) was green), and the design needed to indicate the country of origin.
Every country except Great Britain has always put its name on its postage stamps. But even in the earliest postage stamp designs the idea of national symbols was widely in use. Countries largely used pictures of past or present political leaders on their stamps to identify their place of issuance. But even from the first issues many counties used national symbols rather than people. France used the image of Ceres (a goddess who represented the French Nation) while Switzerland also used an allegorical figure representing the Swiss nation as well as William Tell, the mythological Swiss hero and archer . The reason for these two countries use of allegorical symbols is different. In the case of France, the image was probably used because of that country's painful political situation in the nineteenth century, where they moved from monarchy to republic to empire, back to monarchy, and then back to republic again. This left a very short list of people who had enough broad appeal to put on stamps. Switzerland's case was somewhat different. Switzerland has always been a much looser political confederation of Cantons than most non-Swiss realize, since many of the political decisions that in America are taken at the national level are state decisions in Switzerland. Accordingly, there were few national politicians of sufficient stature to warrant being placed on Swiss stamps.
Interestingly, the United States had it all ways. We had a fascination with dead Presidents (and Ben Franklin) throughout the nineteenth century, but threw in the occasional allegory of Liberty as well. One of my favorite symbols on older stamps was issued by Canada. It is a simple representation of the animal that was the reason for the original colonization of our northern neighbor.