Yo! is good.
hey, I just dragged my ass through some big ass dung mound of art and came across this pretty little gem. It's true that your work needs a little polishing but looking at that not much polishing is needed. I'm no pro myself so I can't say much...but, the colors and the background in this picture are very good. The body shape and the facial features of the characters need refining but you're almost there! I say this is pretty well done.
lol can't help but point out that vocaloid isn't really a game, rather a voice synthesis software, a pretty good one at that. I suggest you look for some songs with the character Miku Hatsune in them...like "Melt".
Good luck with your future work!
CHiao!