Hello, Picasso! We miss art class, too. SignUpGenius subscribers have the ability to build a custom sign up design using multiple images and layouts. If you are in the process of creating the sign up, at Step 2: Themes, you will see a wide variety of premium themes. If you select an existing premium theme, you can then choose “Customize Selected Theme" in the top right corner, and you will be directed to the theme builder area where you can customize the theme you selected. You can also start from scratch by clicking "Tools" on the left side of your Sign Ups page and choosing the "Custom Themes" option.
For more information and tips, view this blog post.