I don't know if anyone has released a custom skin pack. Someone might have, but I personally don't know.
This is the track I've been working on and it is a WIP. It is just an edited version of the Derby Arenas map. There is a "parking lot" behind the garage looking building. I know that there are textures missing in a spot and I will try to fix in the next update. With all that being said have fun! Please give me feed back too. Thanks!