3.1.1 Nether Ore textures
Version 3.1.1 includes textures for Nether Ores and Biomes o' Plenty's Overgrown Netherrack, among others.
Outside (V3.1)
Some of the more noteworthy block texture changes
Menu (V3.1)
Some item textures
Nether (V3.1)
A sample of the moody Nether
Nether Ores
v3.1.8 using multiple mods that add ores to the Nether