[Texture animation on multiple sides of a prim]

What you need to do is make your own cube from 6 prims.
And use 6 textures and 6 scripts, one of each per face. (Or in your case 3)
That's how i did it.
To create textures and scripts you can visit http://www.mrmonke.net/anigifTolsl

It helps you make a tiled texture and also generates a script for that texture.

I am still waiting for 4k textures so i can make some nice long animations.
Or perhaps webm support. LL?