Make sure the logo has a transparent background. This can be done in Photoshop. Save the logo as a .png image.

Click the check mark on the logo and set as margin left 1.

Website header background image (website wide)

Use a background image that has light colors, so the logo will be clear when it's about the background image.

Set the color white as background color. Add the background image and select as the starting position at the top center. The behavior is set to image scrolling and not repeat.

Website header background image (page wide)

No background is the required setting for this section.