I get really annoyed (not really) when I see people draw realistic Eeveelutions but they all look like wolf-like or cat-like or fox-like things that are just slightly less Pokemon looking and all of them pretty much look exactly the same as the cartoon versions in terms of build...
And then the Biologist in me started thinking, 'Well, this is evolution, so technically when Eevee evolves it should be better suited for it's new environment.'
So here I have Jolteon modeled after the anatomy of a Cheetah. Large paws, deep and narrow chest, and a tall frame built for speed. I figure the spikes around the neck/tail could be quill-like hair modifications to ward off other Pokemon, since Jolteon might not have the physical stature to otherwise do so.
For Vaporeon I borrowed blueprints from seals and otters. I still used the basic quadruped form seen in all the Eeveelutions, but I made the body slightly longer and thicker, and the legs shorter and stouter. I figure Vaporeon would need to get those limbs out of the way if it is going to use that powerful tail for speed in the water. Instead of fur I used some rudimentary scale texture... Maybe they aid in refracting light and help Vaporeon 'melt into the water'?
This is why you don't show Pokemon to an anatomy person like me. (Or, this is why people like me love Pokemon!!!)