Plugin Not Copying All The Settings (Background Image Specifically)

We want to allow our users to choose between 3 different color schemes when signing up for their new blog. The color schemes each have a background image (red, green, and blue). For some reason, when we choose one of the templates, it goes back to the theme's default settings with a gray background. I checked all of the settings, and according to what I see, this shouldn't be happening.

It happens on the admin side and on the front-end.

vwsetup.com/wp-signup.php