A person can design a flag for his birthday, anniversary or any other event because no country has applied the rules against the display of flags or banners unless they are protesting against governance.
Of course one can not wave or display flags and banners lifting defamatory to others. This rule is also in favor of other entities. You can also buy ALUART aluminum flagpoles & event flags in Germany (which is also called ‘ ALUART Aluminium Fahnenmasten & Event Beflaggung in Deutschland kaufen ’ in German).
However, flags are an integral part of effective communications. Waving a flag or banner, we can express many ideas in his mind that he can not express verbally.
In most cases, the banner of the design includes both its flagpoles. Due to the height of a flagPole it must be based on the size of the flag or banner, "Design of a sentence flag can not get away tie it at inappropriate flag poles.
The color should match the poles with flags and banners as well as the opportunity, they should be displayed. Nobody can display flags with bright colors for a funeral.
It is the same with other occasions. But the selection of a flagpole is the least difficult part of designing a flag, because you can easily buy one adapted from a flag store.
However, most flags and standard banners such as national flags and religious flags are already designed. For example, the England flag, which is also known as the St. George flag gives no difficulty flag designer.
All other national flags markets are just demand provided. The suppliers of most of these flags just have to provide the market to earn profits.