How To Set The Color Palette And Background Image On A Modern SharePoint Site Using PNP PowerShell

Using most of the scripts for deployment from sp-starter-kit for one new project on SharePoint Online.

I am stuck at the following: If I use the code to set the theme from here -

https://github.com/SharePoint/sp-starter-kit/blob/master/provisioning/functions.ps1

I am not able to set the backgroundimage.

If I use the CSOM web.ApplyTheme method - the spcolor is not doing the same as the powershell script.