Biggy gives you a few header styles. The only exception is that on pages that use a cover banner image, the image will be the background behind the main header.
With regards to the image-based header styles, these are only for blog, page, and front page layouts. However, for the light vs dark header styles (1 and 2), here is how to make the change for your inner pages.
- Go to the Appearance > Customize > Theme Options > Other Options
- Look for the Site Header setting and check the box to use the dark header style.
- Click the Publish button.