You would like a custom background wallpaper.
If you want to customize the background wallpaper that is shown during an unattended Windows installation, you have to replace the original file with your own new wallpaper.
Convert your new wallpaper into the bmp format.
Rename the file into Background.bmp.
Locate the original file in your Microsoft deployment toolkit "sample" directory (%program files%\Mircosoft Deployment Toolkit\samples).
Replace the original file with your own file.
After this you have to update your deployment share and create new .iso and .wim files.
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.