Animated portal textures not filling entire blocks

Hi, I've been experimenting with creating a new dimension and making a portal to make that happen.

I have everything completed in terms of the portal. I recently made an animated texture for it. When I use this animated texture, though, it only shows up in the middle of the portal block. On a 16x16 texture, it's the middle four blocks that show up. On a 128x128 texture the entire texture shows up, but only in the area where the four where when the texture was set to 16x16. I hope that makes sense.

Any help appreciated.