Hi, All.
Take a look how I made an old school motion blur. You may find this technique useful.
Enjoy!

excellent
I dind'nt find a correct way to achieve that.

Thanks, bro. In fact you can make this effect even lighter on the cpu - just use a Billboard Camera and 2 sprite particle systems - one for the actual sprite of the mesh, and the other for the trail. Honestly, I think we should use Sparcle on the second emitter because there we have more control over the tail itself + we can control the tail color/opacity with gradient.