We have a rails app that I recently updated from Rails 3.0 to Rails 3.2. This app services multiple clients. To customize it for each client, we have the directory app
Was able to do it in the application.rb:
require "#{Rails.root}/app/models/settings.rb"
config.assets.paths << "#{Rails.root}/app/themes/#{Settings.theme}/assets/stylesheets"
config.assets.paths << "#{Rails.root}/app/themes/#{Settings.theme}/assets/images"
config.assets.paths << "#{Rails.root}/app/themes/#{Settings.theme}/assets/javascripts"