How do I customize the look/feel of my lock screen? I have a Samsung Droid Charge (running 2.2) and it comes with two lock screen slider styles: Glass and Puzzle. Is there any way to get additional styles? I've done quite a bit of searching but haven't found anything. 

Note that I'm not looking for an app. I'm specifically looking for more system styles, if they exist.

Do they exist?
Try WidgetLocker, it's very customizable and my favorite.