Rails: How to set a background image in rails from css?

In your CSS:

background-image: url(background.jpg);

or

background-image: url(/assets/background.jpg);

In environments/production.rb:

# Disable Rails's static asset server (Apache or nginx will already do this)  
config.serve_static_assets = false

# Compress JavaScripts and CSS  
config.assets.compress = true

# Don't fallback to assets pipeline if a precompiled asset is missed  
config.assets.compile = false

# Generate digests for assets URLs  
config.assets.digest = true

If you have the image in your public directory like public/bg.jpg

background-image: url('/bg.jpg')

If you have image in app/assets/images/bg.jpg

 background-image: url('/assets/bg.jpg')

For sass (scss) this code works with the following image path

app/assets/images/pictureTitle.png

body { 
  background-image: image-url('pictureTitle.png'); 
}

You might also need to restart your rails server.