Every texture file once had a brother. But all brother textures went missing...
Now they're back from the dead in the 'Default's Brother' Resource Pack which adds these textures and some sounds to Minecraft.
The Default's Brother pack has more than one texture for some mobs (like Zombie, Squid, Creeper, Cow, Chicken,...), but you can't see them in your normal Vanilla Minecraft.
You have to install Optifine or McPatcher.
The pack includes textures for the following mods at the moment:
-Just Enough Items 1.10
-Camping Mod 1.10
-Reinforced Tools 1.10
-Not Enough Items 1.8 & 1.9
-Emerald & Obsidian Mod 1.8
-Decoration Mega Pack 1.8
-Whole Tree Axe Mod 1.8
What I'm currently working on:
-Textures for 'Fishing net Mod'
-Textures for 'Biomes O' Plenty'
-Textures for 'Lightning Craft'
-Textures for 'Industrial Craft 2'
Minecraft 1.10 (with mod textures)
Minecraft 1.8 (with mod textures)