it's easy enough to change your banner, all you need is something that opens dds files, photoshop with the dds plugin, or get a free one off the net, open the file with the banners, called banners a, b and so on, and copy another banner and place it over the one you choose, then place that one over the other one, just back up the file incase you mess it up, or you could ask someone to make you a new banner in this thread
http://forums.taleworlds.com/index.php/topic,27335.0.html