Board Thread:Support Requests - Designing Your Wiki/@comment-33747126-20171223071545/@comment-30093946-20171223121714

try changing background through Help:Theme designer first, if you still want CSS /** Background **/ body.mediawiki { background-color: #092140; background-image: url(URL Of Image); background-position: center; background-size: 1275px; background-repeat: repeat !important; }