If you want a different logon screen every time you logon, then you can use Logon Screen Rotator which will automatically do this for you.

Download and install this software from the link given below. Add some images and set the timing for changing the logon screen. Just make sure that the size of image you are adding is not more than 256 KB. You will require .Net framework to use this app.
Download Login Screen Rotator

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