Thread:Gcheung28/@comment-5785681-20150104170534/@comment-5108618-20150106151654

Are you talking about the skin (the image that appears behind the content area itself)? You can upload a .jpg, .png or .gif and the maximum file size is 300 kilobytes. Background images may be divided in half on larger screens (most of the division is covered by the site's content area). Help:Background can help you out if you're trying to do a custom background :)