well done, the track just needs a few more "landmarks" (like the huge oil bottle) to make it stand out a little more and stay fresh as the months/versions go on. To keep the FPS up you may remove a few trees :-)
quick tip:
if you want the skins to show up in ContentManager, put them into a cm_skins subfolder (under the main skins one) so you will be able to freely select which one to use before every race