The best luck I had was having a couple of coloring sheets drawn by Angel Contraras. I know I goofed up the spelling on that one.
www.art4clowns.com (That I can remember.) He is a clown himself and a fantastic artist.
A few friends have tried different programs over the years that supposedly render a line drawing from a regular photo and each and every one looked terrible. Well, maybe not terrible, just not professional in any way. They looked home made. I strive in all my marketing and all my appearances to be as professional as possible.
I have my coloring sheets on the website but have not tried a contest. Not a bad idea.