Where does Windows 10 keep the welcome images?

After installation, and for a few days, Windows 10 starts by asking you if you like a series of images that appear when you start the computer, then, based on your opinion, a selection of these images keep "welcoming" you. I'd like to know where these images are saved (and how, if it's a database or a change of format-extension).

I might want some of them, I might want to add a few of my own.

Does anybody know the path to these images (or database)? Is there documentation or options in Windows 10 to treat them?

Thanks to Anant Milk now I know this is called the Lock Screen. Knowing that, I found the answer in google: http://www.tenforums.com/customization/5428-windows-spotlight-lock-screen-image-location.html

The path to the images in Lock Screen (and some others used by the system) is

C:\Users\{your name}\AppData\Local\Packages\Microsoft.Windows.ContentDeliveryManager_cw5n1h2txy‌​ewy\LocalState\Assets 

Rename extensions to jpg and you can get them.