Overall, for your second scratch sprite, I think this is pretty good. I think, especially in the head, you've accurately captured the essence of an Eeveelution. Also, I do like the concept!
However, there are several things you can improve. The biggest problem, imo, is that the sprite is almost a profile. I see the head is almost turned toward us, but besides that, the body isn't. Looking at the official Eeveelutions, notice how they all have a 3-D perspective (that might be the wrong terminology--sorry!). Also, there are only two visible legs. Looking at the official Vaporeon, even though it's sitting, you can still see both front legs. I think that if you find a way to incorporate another front leg, by either repositioning it's front half or something, then you would also add that necessary perspective. I think you could also improve the hind leg by making it slightly thinner at the ankle.
Finally, I really like the concept of the blue flames running down the Eeveelution's back. They're very characteristic of the Dragon type, but I feel you could exaggerate them more by making them bigger and give them more random forms. For example, look at Moltres's sprite--I think the flames on it's wings aren't huge, but they still accurately represent fire on a more reserved scale.
Overall, this sprite is very good, especially considering this is only your second scratched sprite. I know I said it earlier, but I really think the face is excellent.