Sometimes you need inline images in your single page...

application_helper.rb

module ApplicationHelper
  def inline_image image_path
    result = Rails.cache.read "InlineImageBase64::#{image_path}"

    if result.present?
      result
    else
      ext = File.extname image_path
      image = File.open(Rails.root.join("app/assets/images/#{image_path}"), 'rb').read

      result = "data:image/#{ext};base64,#{Base64.strict_encode64(image).strip}"
      Rails.cache.write "InlineImageBase64::#{image_path}", result
      result
    end
  end
end

somepage.html.erb

<!-- some html code -->
  <style type="text/css">
    .some_class{
      background: url('<%= inline_image 'inline/some_image.png' %>') no-repeat top left;
    }
  </style>
<!-- some html code -->