Copyright issues

As a cake decorator I get plenty of requests for designs and concepts for cakes. Most of the time people will just point at a novelty cake in the book and say they want that one. Some people will be vague and only tell me what colors they want, or they want flowers. People have also given me pictures to use with our Edible Images scanner and printer, or asked me to simply draw certain things. I am pretty good at drawing, and it's easy enough to use the scanner and printer. But it has come up recently at work that I need to be much more careful about what I let people put on cakes. It's unlikely to be much of an issue with cakes that will just be taken home and enjoyed by a small family. But you just want to protect yourself wherever you can. I've made cakes in the past that used images from cartoons, logos of sports teams, and also designs on napkins or paper plates. I've taken pictures of these, but I've decided not to post them if I believe there will be an issue with copyrights.