Hi @Premita ,
Thanks for the post.
Could you please provide me some screenshots about the error reports after using this PowerShell command?
If you want to customize the header background image of your SharePoint online site, you could design with SPFX.
You could refer to Echo’s answer: Add custom background them for a SharePoint site header
I hope I can offer you a better experience next time if I have a chance to work with you again.
Yours faithfully,
Renjie Sun
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