Don't mind if I express a bit of opinion ya? :)
I think your vector is quite good but there's spaces for improvement. For example, when you vector the lighter part of Kyou-kun's hair, you can reduce its opacity to make it look more shiny. Same goes with the lighter part of Kyou-kun's face.
Your vector line is smooth, no jagged parts which is really good as this is your second vectored wallie. The line of his nose is a bit off. And maybe you might want to remove the flowers on the left side of the wallie.
Put all those things aside, you really made a good wallpaper. I think the background is nice too! Keep it up ya and I'm sure you'll be a great waller someday! :D