For my exams and quizzes, I print them on colored paper, and I usually try to make them aesthetically appealing with the design. I include pictures that are usually relevant to the material they are being tested on. I sometimes include funny cartoons.
I do this because I think it makes taking quizzes and exams an experience that is a little more relaxing and fun than if I just had plain white paper with no images. I also enjoy seeing my students chuckle at a funny picture or cartoon. I teach undergraduate mathematics, and given that many students have math anxiety, I like to try to take the edge off of that.
Has there been any research done on whether or not having colored paper or images on exams and quizzes are beneficial or detrimental?