Oh, and one more thing:
One of the most important rules in heraldry - regardless if it western japanese - are the Rules of Tincture. In West it means colours can only be put on others if they are different sorts, colour and metal. Metals are silver (white) and gold (yellow), and the colours are red (sanguine), black, blue, green... some other colours I don't remember, and occasionally purple and brown. You shouldn't really put metals on metals or colours on colours but pfft that. I don't know the rules of tincture in japanese heraldry, but I bet there are some.
This is because colours should be as discernible as possible. This also why Joel's flag:
is not so good. You can't recognise it easy, because the colours are too dark. Maybe you can make the red more clear.
