Well, Eevee is based on surroundings... Try training him in different Places... Or using stones(like a Moonstone, it doesn't really evolve eevee though)... In pokemon, Platinum, Pearl, and Diamond the Mossy Rock and the Icey Rock are to be touched when Eevee is in the front of the party! Then train him in a Forest(if you touched Mossy Rock) or in a Snowy Blizzard(if you touched Icey Rock) then he will evolve in to... Or you should see for yourself... Have Fun!

Spoiler: Be sure to highlight the Words on a computer to see what it says!   Train Eevee at full love (only in Platinum, Diamond, and Pearl) during Morning or Night to get a Special Eevee Evolution...