David Airey has a great little tutorial up on how to modify your WordPress login page, so that it fits more in line with the style of your site.
Even better, it is basically just the modification of two image files. So check it out. He seems to be using this as a way to remind his customers of the work he has done for them, by repeating his brand every time they need to log in. A very wise move for those trying to really get their name out there when it comes to customizing WordPress.