In the recently released Windows 10 Technical Preview Build 9926, there are few new experiences which are not explicitly enabled to users. Microsoft will be enabling it to the general public as the code gets matured. If you are interested to check out the experimental stuff, you can do it by modifying your registry.
The redesigned login screen experience is one such thing which you can enable by following the steps below.
1. Open
Registry Editor.
2. Go to the following Registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI\TestHooks3. Double click the Threshold DWORD (32 Bit) value and
change the value from 0 to 1:

4.
Restart your PC.
That's it. You are done. Here is how the new logon screen looks like:

When you are logged in but locked your PC, it shows the tiny chess knight icon near the clock.

But when you are signed out, it shows the mirrored chess knight icon:

This tweak affects the CTRL+ALT+DEL security screen as well.
To reset the login screen back to the default, simply repeat the steps above but change the value of the 'Threshold' key from
1 back to
0.
source:winaero