I'm pretty sure ZUN wouldn't care. As far as Kongregate caring, if the music which you are using isn't a violation of the rules, using the original sprites wouldn't be either.
I am the bone of my sushi. Rice my body, and soy sauce is my blood. I have eaten over a thousand meals. Unknown to hospital bills. Nor known to physics. Have withstood platforms to bounce toward many kinds of sushi. Yet, those paws will never hold chopsticks. So as I dine, 'Unlimited Sushi Works'.