Board Thread:Support Requests - Getting Technical/@comment-38452727-20190411134115/@comment-24931587-20190411203349

Adding the following to your wiki's CSS will set the background and outline for the infobox title (.pi-title), group headings (.pi-secondary-background), and field labels (.pi-data-label):

.portable-infobox .pi-title, .portable-infobox .pi-secondary-background, .portable-infobox .pi-data-label {   border: 1px dotted #533a1c; background-image: url(https://vignette.wikia.nocookie.net/the-vampire-massacre/images/9/9a/The_Vampire_Massacre_%28Orange_Infobox%29.png/revision/latest?cb=20141108065246&path-prefix=pl);

}

You can find info about CSS for portable infoboxes at Help:Infoboxes/CSS.