The odd thing is, they don't all really say the same thing. Most of them say come up with a concept so that must be good advice ... except that it really seems almost the same as come up with a character. So, I'll help you out a little bit by talking about some actual methods by which characters are created.
The number of stars on the flag is fixed at 12, and is not related to the number of member states of the EU (although the EU did have 12 member states from 1986 to 1994). This is because it originally was the flag of the Council of Europe.
It is widely known that the 50 stars on the flag of the United States represent the states themselves. When the Stars and Stripes was adopted in 1777 there were 13 states (then colonies), thus a 13-star flag, and as each new state was admitted to the union a star was added to the flag.