I’m flogging the ‘Connections’ theme that I downloaded from WP. The image URL is in the CSS, not the PHP. I put a static link to css.php in index.php (which is where it started), and it changes every time you refresh the page.
https://blog.kumapageworks.org
I’m sure there are better ways to do it – but it works. I think maybe tomorrow I’ll split the CSS files into two imports to save bandwidth.