Yeah sorry I though you meant a horizontally slung banner, but it will work with anything. Yeah you could turn the texture round it may give you a nice flowing look. But this technique is pretty versatile for what you want to do.

Another tip is, that the more of the fabric displacement map your flag banner takes up the more of the folds you'll see, as you can see in the banner I did, some of the nice folds in the flags are missing because its a lot thinner and those folds displaced off the banner.