Backstretch allows an image or images to appear as a background. To enable backstretch, navigate to Appearance > Styles > XenForo - UI.X > Style Property Groups > Style Properties: [UI.X] Global Settings. Check the box next to Enable Backstretch.
You can add or remove backstretch images below. Your images must be wrapped in quotes and when using images, every line must be followed by a comma except the last image. Your Backstretch Selector allows you to adjust where your backstretch images are applied to. Enter body if you'd like the backstretch to be applied to the entire document. Backstretch Duration and Backstretch Fade allow you to adjust how long an image appears for and how quickly it fades away. Enter these values in milliseconds.
To adjust your maximum page width, navigate to Appearance > Styles > XenForo - UI.X > Style Property Groups > Style Properties: [UI.X] Global Settings. Enter your desired width in pixels or as a percentage within Max Page Width.
If width toggle is enabled, your max page width must be set as pixels.
Width toggle allows your users to toggle the width of your forum between fixed and fluid (I.E. it enables and disables the Max Page Width style property).
To enable this setting, navigate to Appearance > Styles > XenForo - UI.X > Style Property Groups > Style Properties: [UI.X] Global Settings and check the box next to Enable Width Toggle.
To change your UI.X Page Style, navigate to Appearance > Styles > XenForo - UI.X > Style Property Groups > Style Properties: [UI.X] Global Settings.