Although I think that alket is referring to animated ground textures. I think this would have very limited usefulness. However, if ever implemented, GIFs are probably a bad idea. They're limited to 256 colors, which hinders quality (although might not be a big issue since ground textures tend to use a small number of similar colors). More for consistency than quality, animated ground textures could be implemented like water textures currently are.
But again, I'm not sure how useful these would be. It seems like proper use of animated objects and particles for those objects, combined with tileset fog would be better looking.