Customize the OS appearance according to your taste and preference in this section. You can personalize lock screen, start screen and account picture here.
How to Access It ■ Invoke Settings Charm either through
the Charms Bar or key combo
Win + I.
■ Select Change PC Settings option located at the bottom of
the Settings Charm pane. This will launch PC Settings.
■ Select Personalize tab from the left pane of PC Settings.

The lock screen is one of the most beautiful features in Windows 8. You can change the wallpaper of the screen in this section.
Besides the wallpaper, lock screen also shows small widgets that show notifications from their corresponding apps. Eight such widgets can be placed on the lock screen.
The apps for those widgets can be specified here. Out of those widgets, you can select one widget that can show detailed notification. My favorite one is the calendar app, which can show me important reminders on the lock screen itself.
Start Screen
This section lets you customize the Start Screen. You can select color scheme as well as the background pattern from a limited array of schemes.
Account Picture
You can either select a photo from your existing collection or click a new spontaneous one through the camera, of course, if you have any.
source:windows8update