Redirect local sand-boxed Drupal file requests to a development server. This helps avoid having to sync (sometimes, very huge) file structures onto your local machine.

gistfile1.nginxconf

### Apache Rewrite
  # Request resides in your 'sites/default/files' folder.
  RewriteCond %{REQUEST_URI} ^/sites/default/files/(.*)$
  # File doesn't exist.
  RewriteCond %{REQUEST_FILENAME} !-f
  # Directory doesn't exist.
  RewriteCond %{REQUEST_FILENAME} !-d
  # Redirect request to your development or production server.
  RewriteRule ^/sites/default/files/(.*)$ http://dev.example.com/sites/default/files/$1 [L]

### nginx Rewrite
  ## Try local files first, otherwise redirect to a development server.
  location ^~ /sites/default/files {
    try_files $uri @dev_redirect;
  }
  ## Development Server Redirect
    location @dev_redirect {
    rewrite ^ http://dev.example.com$request_uri? permanent;
  }