Allow inline style attibute on element using Content Security Policy (CSP)

Well, in this case I'm imagining that there is a form, with exclusive administrative access, where the image and its path name is informed, updating the database, and a query with "limit(1)",.
It's a purely personal choice, but using PHP in CSS files is unusual, base_url is intrinsic to the path to be given, if you put '/img/filename.jpg', the server automatically adds "https://example .com" in front of the first segment: https://example.com/img/filename.jpg. It is important that you understand that inside the css there will be a PHP variable that needs to be "converted" by the PHP server that also needs to know the source of "$sliderimages", etc.

You decide!