Attempt to load files from production if they're not in our local version. Src: http://stevegrunwell.github.io/wordpress-git/#/13

.htaccess

<IfModule mod_rewrite.c>
  RewriteEngine on

  # Attempt to load files from production if they're not in our local version
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule wp-content/uploads/(.*) http://{PROD}/wp-content/uploads/$1 [NC,L]
</IfModule>