A custom background image must meet the following two requirements:
Filename: pba_bkgd_image.png
Size: 800 pixels wide by 600 pixels high (800x600)
If you want to customize the default pba_bkgd_image.png rather than create a new file, complete the following steps to retrieve a copy of the default image file:
On a managed device that has ZENworks Full Disk Encryption enabled (no policy needs to be applied), locate the fsebrand.bin file:
c:\windows\nac\sbs\fsebrand.bin
Make a copy of the fsebrand.bin file and rename it to fsebrand.zip.
Extract the contents of the zip file to a location outside of the c:\windows\nac\sbs directory.
The contents are extracted to an fsebrand folder. The pba_bkgd_image.png file is located in that folder.