module ActionView
  module Helpers #:nodoc:
    module AssetTagHelper
      def image_path(source)
        if File.exists? [RAILS_ROOT, 'public', 'images', I18n.locale, source].join('/')
          compute_public_path(source, "images/#{I18n.locale}")
        elsif File.exists? [RAILS_ROOT, 'public', 'images', I18n.default_locale, source].join('/')
          compute_public_path(source, "images/#{I18n.default_locale}")
        else      
          compute_public_path(source, 'images')
        end
      end
      alias_method :path_to_image, :image_path
    end
  end
end

module ActionView
  module Helpers #:nodoc:
    module AssetTagHelper
      def image_path(source)
        if File.exists? [RAILS_ROOT, 'public', 'images', I18n.locale, source].join('/')
          compute_public_path(source, "images/#{I18n.locale}")
        else
          compute_public_path(source, 'images')
        end
      end
      alias_method :path_to_image, :image_path
    end
  end
end

Patches Rails 3 to automatically look for images in a folder corresponding to the current locale (under 'images', ie: '/images/en'), and falling back first to the folder of the default_locale, and then to the main images folder ('/images') if the image was not found in the locale folder. Put any localized images in their corresponding folders ('/images/en', '/images/es', etc.) and any non-localized images in '/images'. No need to specify anything special in the view, just use image_tag as usual.

Automagically find localized images

Rails