Another close cousin of convention is 'fashion'. Fashion is a 'closed convention'. It allows you to be both conventional and different at the same time. It means that your convention is different from the conventions of the masses. It even gives you a license to put down other conventions without having any good reasons to do so.
Fashions can be creative, in fact they usually are for a short period of time.
Eventually, they become scorned as being 'old hat' and melt back into the quagmire of mass convention. One of the main attributes of all things conventional is that of not standing out. Convention reveres in being lost within itself. Of course, in standing out from convention, you can stand out like a jewel in the desert or stand out like a sore thumb. The distinction is merely a matter of viewpoint.