If you want to to add a single large image, always make sure to optimize its size.
If you are not using Chamaileon yet, you can register here and change the background of your email.
Here are the steps with screenshots on how you can change background in the Chamaileon editor:
Click on the ''Body'' in the breadcrumbs.
2. In ''Element background'' change the background color.
In Chamaileon, we also have advanced features like options to position and repeat the background image. You can choose weather you want your image to be at the top left, top right, bottom left, bottom right corner.
If you are not using Chamaileons' advanced HTML email editor yet, you can register here for free and change the background of your email.