Many people who use custom themes or launchers are familiar with WidgetLocker. What many people don't realize, though, is that customizing WidgetLocker itself is a fairly straightforward task. Better still, there are plenty of existing customizations available, meaning that you have to do little more than shove your modified .PNG files into the APK.
Before / After
Dalton Gore - better known as @colormeandroid - is responsible for gathering the individual mods and creating the guide. While the guide is a little too light on details for newbies, it does provide the luxury of choices - he provides instructions for 5 methods: