application.html.erb

<%= css_theme('default.css','scaffold.css') %>
<%= js_theme('default.js','testtwo.js') %>

<%= link_to img_theme('logo.jpg', :alt => 'Back to the homepage'), root_url %>

application_helper.rb

  def js_theme(*files)
    file_array = [*files]
    js_array = []
    file_array.each do |row|
      js_array += current_theme_path('js', row.to_s).to_a
    end
    javascript_include_tag(:defaults, js_array)
  end

  def css_theme(*files)
    file_array = [*files]
    css_array = []
    file_array.each do |row|
      css_array += current_theme_path('css', row.to_s).to_a
    end
    stylesheet_link_tag(css_array)
  end

  def img_theme(file, options)
    image_tag(current_theme_path('img',file), options)
  end

  def current_theme_path(type, file)
    path = "/themes/" + @opt_default_theme + "/images/" + file if type == 'img'
    path = "/themes/" + @opt_default_theme + "/stylesheets/" + file if type == 'css'
    path = "/themes/" + @opt_default_theme + "/javascripts/" + file if type == 'js'
    return path
  end

site.html

<link href="/themes/default/stylesheets/default.css?1263252884" media="screen" rel="stylesheet" type="text/css" />
<link href="/themes/default/stylesheets/scaffold.css?1263252968" media="screen" rel="stylesheet" type="text/css" />
<script src="/javascripts/prototype.js" type="text/javascript"></script>
<script src="/javascripts/effects.js?1263578224" type="text/javascript"></script>
<script src="/javascripts/dragdrop.js?1263578224" type="text/javascript"></script>
<script src="/javascripts/controls.js?1263578224" type="text/javascript"></script>
<script src="/javascripts/swfobject.js?1263578224" type="text/javascript"></script>
<script src="/themes/default/javascripts/default.js?1263578286" type="text/javascript"></script>
<script src="/themes/default/javascripts/testtwo.js?1263587716" type="text/javascript"></script>
<script src="/javascripts/application.js?1263578223" type="text/javascript"></script>


<a href="http://localhost:3000/"><img alt="Back to the homepage" src="/themes/default/images/logo.jpg?1263252935" /></a>