Any picture that can be designed on a computer can be used on iron-on transfer sheets. The main factor that affects whether or not the image will stick to the fabric depends on how the picture is applied to the shirt.
HP offers a product called Cool Peel, which allows its users to create images on their software and print them out using the special transfer paper. Once an image is created, it will need to be inverted in order to be printed in the right direction.
After creating and printing an image, the user needs to properly iron the image onto the t-shirt. To apply the image using an iron-on transfer, heat the iron using the highest setting, press down on the iron to generate 50 pounds of pressure and evenly apply the iron-on image so it sets properly.