It's quite the rarity (heh) to find a black and white piece that manages to catch my eye from using a TON of blacks. It stands out very well from the usual colored works you see.

I kinda like this pic despite not coming from a Mexican cultural background to have some sort of attachment to the image you just ponified. Rarity seems to be the best pony to pick for this as she does have something for really big hats. Perfect pony of choice for this, I would say.

The approach may have been better though. You can see the quality of linework in the original parts of this image and see that it looks kinda messy - something I would expect from human hands using ink on a piece of paper. The vector you took is a vector - computer drawn based on a set of anchor points. Vectors are very very smooth - much smoother than what I would ever achieve with a sharpie and paper. The difference in line quality makes Rarity appear to be in a different art style, so you have things that doesn't seem like they belong. It is probably better to try to replicate the line textures from the original image and trace the vector.

Going another route to draw the vector to replicate the texture would also let you do other things such as giving Rarity's hair more depth - the producers gave her hair gradients for the sole reason of creating enough depth to make her hair look less like a senseless blobs.

You also kinda cheated with the gray shade for her cutie mark as the original image has no such gray shade.

Then, there's the hatching (that's what I think it's called) as an attempt to create an illusion of a middle shade to stand for Rarity's eyeshadow. If you ask me, there are two ways of seeing this - either a middle color, or a bunch of eyelids piled on top of each other. It is likely far better to use much thinner but much denser lines.

Then, there's the shading. It doesn't appear that consistent (not that the original image was any better). The shadow under her jaw suggests that the sun is very high and a bit behind us, but the shadow under her lower mane suggests a sun even higher and not behind us. But... with a sun that high, wouldn't her large hat get in the way? Well, since the original image doesn't seem much better off with shading coherency with hats not blocking the sun as it should, but I believe at the very least, we could try to shade her had in a way to emphasize a bit more roundness to stay more true to the style of the original image, maybe also darken her inner ear.

Using a flat vector isn't really staying true to the original art style as vectors are smoother and flatter than the original image. But eh. This piece is awesome in another way for just having large areas of dark blacks and bright whites that just seems to catch my attention.