Yup. When loading the OS into NTLite it creates a TEMP OS on the C:\Temp\NLTmpMount01. Inside this is the OS that NTLite will be tuning. Close NTLite but DON'T unload the OS.
Before you go all Rambo on this, it has stages. First create the pics below. Don't create the files that doesn't exist, you do not have to create them. You need to look inside the folder to know.
Create your image in paint as 448 x 448 save it as a BMP file and again as a PNG file, name the files user.bmp and user.png.
These you don not have to create a BMP of,
Resize the image to 200×200 and save as User-200.png
Resize the image to 40×40 and save as user-40.png
Resize the image to 32×32 and save as user-32.png
Resize the image to 48×48 and save as user-48.png
Resize the image to 192×192 and save as user-192.png
If you want to manage the guest account pictures replace guest.png and guest.bmp with the 448 x 448 copies of your image and name it accordingly.
The various sizes makes the images visible in various places such as the top right corner (smaller image), the login screen etc.
You need to take ownership of the folders before you edit or change to contents. I included the ownership reg file, it add's it to the right click context menu. Un-rar and double click it and agree to all.
Copy your lock screen personal images, the small ones, to C:\ProgramData\Microsoft\User Account Pictures\
NOTE: Replace all the user images with the exact same formats and sizes. Keep the name structures and replace the ones inside the folder. Delete any .dat files in the folder.
The lock screen background. This I have not tested since I remove mine, but they are located at,
c:\Windows\Web\Screen\
Replace them with yours but make sure the file names remains the same along with what I assume the pixel size (I think).
The background is a little trickier. They are stored in 3 places, most of the time only 2 but I replace all three if the third exist.
c:\windows\Web\Wallpaper\Windows\ is the one, img0.jpg. Keep the name structure, the size is not important. You can also add additional images in the following folder should you want to use the sliding screensaver.
c:\windows\Web\Wallpaper\
Then the next one is in the following folder. Again, keep the name structure and the size is not important.
c:\Windows\WinSXS\amd64_microsoft-windows-s..l-wallpaper-windows_31bf3856ad364e35_10.0.17763.1_none_cbd8101a089b2adb
The third place I have found on one machine and it's at. Again, keep the name structure and the size is not important.
c:\Windows\WinSXS\amd64_microsoft-windows-s..l-wallpaper-windows_31bf3856ad364e35_10.0.15063.0_none_ec25ff6de9407847
IMPORTANT: Empty the recycle bin, agree to all to delete before you restart.
Then just restart since the files you removed will be cached and NTLite complain and WILL NOT finish the rip. Some say just refresh explorer but it is not always released. After restart go back into NTLite and apply your settings and finish the rip.
Done