Settings - Tabs (Background)

Solid
Image
Bing
Wallpaper

Select background type.
Solid specifies a single color background.
Image specifies a bitmap background.
Bing specifies Bing image of the day. Internet connection is required.
Wallpaper specifies that the desktop wallpaper will be used as the background image.

Color

Select color for solid background type.

File

Specifies background image file for image background type.

Relative

If checked, background image will be relative, i.e. when moving the window, it will appear that it's move above the background image.

Position

Select image position from the list. Background image can be centered, stretched or tiled.
"Fit" and "Fill" options generate a stretched image, keeping aspect ratio.

Extend across monitors

If checked, background image will centered/stretched/tiled across multiple monitors (if present)

Tint color

Select tint color for image and wallpaper background types.

Tint opacity

Set tint opacity for image and wallpaper background types.

Inherit

If checked, the tab uses inherited backgroud.

Set as default

Set the current tab's backgroud as default. Tabs, having Inherit checked, will use this background.