Glowstone/Lightgem cannot have it's animation customized using a .txt file in a custom Texture Pack.

Creating a .txt for lightstone.png (glowstone texture) doesn't change it's in-game custom animation.

Attached within is a custom glowstone texture to test it out, along with a .txt file. Just add it to your snapshot .jar ("/texture/blocks" folder) and replace the existing ones.