Add background and icons to DMG image

[JMCanning78]

Looking at the DMG for Docker, it appears that you can specify a background for the disk image by creating a .backgrounds directory and placing an image file in it.

$ ls -aRF /Volumes/Docker/
./			.VolumeIcon.icns	Docker.app/
../			.background/
.DS_Store		Applications@

/Volumes/Docker//.background:
./				docker-dmg-background.png
../

The .VolumeIcon.icns is not the icon shown for the DMG. Maybe it contains the icon for the Applications folder?
The Applications link is what might be expected:

$ ls -l /Volumes/Docker/Applications
lrwxr-xr-x  1 shakumantpres  staff  13 Jul  5 05:42 /Volumes/Docker/Applications -> /Applications

This task is to create some nice image for the background of the DMG, and maybe add the soft link to the Applications folder for people who want to install it there.