Hello, Picasso! We miss art class, too. Gold and Platinum subscribers have the ability to build a custom sign up design using multiple images and layouts. If you are in the process of creating a sign up, on the Design tab you will see a wide variety of premium themes. If you select an existing premium theme, you can then click the orange Customize text beneath the thumbnail image. You will then be able to customize the theme colors and images as desired.
You can also start from scratch by clicking Tools on the left side of your Sign Ups page and choosing the Custom Themes option. Custom Themes can be assigned to a sign up from the Design tab.
For more information and tips, view this blog post.