By similar do you mean you used any of his, or anyone else's textures? Or did you start from scratch and just mimic is drawing style? The latter you do not need permission (unless you literally traced the image). The former though is not allowed, and you will need permission.
Props for asking. You have restored my faith in humanity.
So as long as the textures aren't exactly the same pixel by pixel I am safe?
As long as they are different enough to where they cannot be easily mistaken for the other. Anything that's so similar that one could easily assume that you just edited Vattic's work would not be allowed. There has to be a significant difference, enough that there is no reasonable suspicion of editing or theft. In other words, if you're going to change a few pixels to try to skirt the rules, don't bother. On the other hand, if the style is similar but the textures themselves are different then that's fine.
^ This. They're definitely different enough that I doubt you'll be accused of theft.
But yes, you need more shading, even to fit with Faithful. If you look at Faithful's textures, you'll see that he uses bands of different shades of color on his weapons to make the swords pop and give them a sense of depth and form despite the fact that they are, for all intents and purposes, flat. This mirrors the default which uses a line of pixels down the center to create a ridge in the center of the blade, making it appear to have an angular blade shape.