I don't find the control center but only a simple system setting window. How to make it more complete than before? I search for login screen setting, and I don't find it. Someone can help me? I'm still beginner and wanna learn more for Linux especially Ubuntu.
Changing Your Session Type
To change your session type and get a different GUI, log out. Then you have a login screen. It's not necessary to change anything in your settings, nor is it necessary to disable automatic login (which I presume you have enabled).
To log out, click the Ubuntu logo icon at the upper-right corner of the screen (the same one you click to access System Settings), and click Log Out....
On the login screen, you can select your user and log in (with your password--the one you set up when you installed Ubuntu, the same password you'd use to unlock the screen or install software). You can also select your desktop environment.
Selecting a More "Classic" Session Type
Ubuntu 11.04 was the last version that had GNOME 2. After that, it's been GNOME 3. Ubuntu Classic was a GNOME 2 interface, and thus has not been supported since then.
However, a GNOME Fallback session is in many ways (not all ways) similar to Ubuntu Classic; you might like that interface. You can get this by installing the gnome-session-fallback package. Then select GNOME Classic for "Desktop environment" on the login screen.
Both desktop environments have traditional design--expanding, nested application menus and a window list embedded in a panel.
Getting More Settings (Like the old "GNOME Control Center.")
The old version GNOME Control Center is no longer available in Ubuntu 12.10. The new System Settings have replaced it (coalescing into its current form over the last few Ubuntu releases).
As Rinzwind suggested, you can use Ubuntu Tweak (more info here) to get a variety of additional handy settings--but as Rinzwind said (and can be confirmed by looking at the categories of settings available), it doesn't add much that's related to user accounts.
Fortunately, the old Users and Groups utility is still available. (This dates back from even before the GNOME Control Center itself was introduced. It's still around because other supported desktop environments--Xfce and LXDE--don't have GNOME's control center.)
The old Users and Groups utility is provided by the gnome-system-tools package.
To run it, press Alt+F2 and run