The back panel design that I created myself, which I think looks quite good, has also been taken by another HAM to modify and use. I'm sharing it here with HamCQ as well.
PS file:
Download
Note: This page can be freely modified and used without requiring any authorization.
The layout is shown below:

Actual results can be seen here:

Other HAM-modified layouts:

Some suggested modifications and known shortcomings:
- There is no space provided for writing notes or comments.
- There is no reserved location for a return confirmation QR code.
Welcome everyone to use my layout and share your modified versions!