Hello guys. Here is a small guide which is going to allow you to obtain trail which may correspond with your country.
I didn't obviously make everything flags, it asks too much time, but I'm going to try to update this guide to add to it. I put you the screenshots of every available trails.

America: http://i.imgur.com/t16RxxU.png
Italia: http://i.imgur.com/bgxsqgE.png
Espagna: http://i.imgur.com/zpVmgXf.png
France: http://i.imgur.com/eBOtjXr.png
Swedish: http://i.imgur.com/iTXiPgs.png
Brasil: http://i.imgur.com/HIklilD.png
Germany: http://i.imgur.com/flOg2lI.png
China: http://i.imgur.com/fOiYNfe.png
Canada: http://i.imgur.com/Clp8DTD.png
Pirates (Bonus): http://i.imgur.com/vWC4vaW.png

To replace a trail it's easy, it's enough to take the file "RainbowParticle.xnb" of your choice which you will find in the file .rar downloadable here: https://mega.nz/#!hQVFgARb!5H_8Z7y4oqIqvimmhh6ocg4ohoTQQPTTjLEU0stX3Bg
Then put it in the following location:
"C:\Program Files(x86)\Steam\steamapps\common\SpeedRunners\Content\Sprites"
or
"C:\Program Files\Steam\steamapps\common\SpeedRunners\Content\Sprites"
If you have any questions or propositions, tell me.
Sorry if my english is bad.
Enjoy! :>