I made a couple of vectors some time ago.
Unfortunatly all of them were deleted yesterday, but I don't understand the explanation. I will ask the mods. Until than I upload my vectors here.
Please leave a comment.

Michiru (Sailor Neptune)

Kyouya & Tamaki

Sakura

Mai & Natsuki (Mai Otome)

Haruhi, Honey & Mori

Mai (Mai HiME)

Angry Natsuki (Mai HiME)

Natsuki (Mai HiME)

Arika & Mashiro

The vectors are rather poorly done. Curves are not smooth and visually it can be seen that it is made from straight lines instead.

In some parts, the curves are quite shaky and inconsistent. There are also breaks in the curves where the straight lines meet.

Bezier curve tool is your friend.

Those vectors were deleted for the reasons kiopi just stated. Vectoring is not an advanced technique by itself, and vector submissions also need to have a minimum of quality. I suggest you learn more about the pen tool.

Did you submit these in the Doujinshi category rather than the Vector one?

Anyway, some of those vectors are better than others. I think those two for Ouran are alright, but the ones for My-HiME need a little more work. I think generally, your CG block colours are for the most part, clean and smooth, it's your outlines that need some work. Try using slighting thicker outlines, and make sure they're smooth and connected. Or, don't use outlines at all.

Hope that helps somewhat. Don't get discouraged, keep on practicing with the pen tool

Kiopi-san has the point ^
Outlines are rather shaky and while they're probably done by pencill you should try pentool or a brush.
There are lots of tutorials to look and why don't you go and have a look.