I like the fighting, bug, poison, and rock-type ones; however I honestly think I've seen better for Ghost and Flying. Dragon is probably the least likely type to ever happen. (I admit, bug is just as unlikely, but it still looks neat.).
I honestly think Poison would be a very good way to go. Eevee's different forms are all about "adapting". So what would happen if it adapted to a highly polluted environment? Steel would probably make a good match to release beside it. Go with sort of an industrial/urban setting.
I like the ground type. Staring straight in to the eyes of his nemesis like a badass even if their are closed. I also like the poision, rock, and steel types because they are pretty kick-ass as well. But I like that most of the eevee_loutions don't have an over use of their types in their design, and i also don't like how the ghost one looks like, it does not seem like it should be a ghost type, looks more like a dark/ghost type. Other than that their all pretty cool.
Eevee himself is a normal type, y evolve into another normal type? i mean, type evelutions are normal like Pikachu-Raichu (electric-electric) but i think the point of Eeveelutions is to have one of every type, making it redundant to have another normal type .......but other than that, everything looks pretty cool