If the design of Apple's Mac OS X login screen just isn't floatin' yer boat, Visage Login might be worth a look. With two separate versions - one for 10.4 and another for 10.1-10.3 - this is one of the few apps I remember where 10.3 users have some features to brag about over Tiger users. As an app for 10.4 Tiger, Visage Login allows you to alter the login screen's logo and desktop image, while a preference pane for 10.1-10.3 has the ability to run screen savers as your desktop background, personalize system alerts, randomize the login screen background, and more.
Visage Login is shareware with a fully-functioning 3 day demo. A single license costs a mere $4.95, while a 50+ machine license for businesses and corporations is $29.95.