Is there a way to use a local url when my assets are stored in an S3 bucket?

I have a bucket I'm pointing to and in there I have a folder called backgroundImg with a background.png

I'm trying to access this from my CSS like

background-image: url('backgroundImg/background.png');

But it cannot find this url. It's building the url localhost/assets/backgroundImg/background.png

Is there any way to use the local path instead of an insanely long s3 url that is hardcoded?