nginx.conf

# Nginx cache busting rewriter, best used on assets that have long-lived expires.
#
# Rewrites like so:
#   blah.com/release_ab2ea212312.../file.css => blah.com/file.css
#
location ~ ^/release_(.*?)/ {
  rewrite  ^/release_(.*?)/(.*)$  /$2  last;
}

paperclip_init.rb

# A paperclip initializer, place in config/initializers/

Paperclip::Attachment.interpolations[:release_path] =
  lambda do |attachment, style|
    unless AssetVersion.version.blank?
      "/release_#{AssetVersion.version}"
    end
  end

some_model.rb

class SomeModel < ActiveRecord::Base
  has_attached_file :image, {
    :styles => {
      :thumb => "100x100",
    },
    :url => ":release_path/attachments/:class/:attachment/:id/:style/:basename.:extension",
    :path => ":rails_root/public/attachments/:class/:attachment/:id/:style/:basename.:extension",
    :default_url => "/images/:class/:attachment/missing_:style.png",
  }
end