Help please its on copyrighted stuff!?

ok well im in this chess club and im the t-shirt Designer.we need a shirt for Competition. well our mascot is a snake and well i went on the internet and searched for a cartoon snake. i found one and drew it out myself i didn't trace it. then i thought i would change it just a little so it wouldn't look exactly the same. so in a way its different i even changed the color. will it be considered stealing. i haven't turned in the shirt so if is considered stealing please tell me so that i may dispose of it. wat should i do!!!!!???????