Board Thread:Support Requests - Designing Your Wiki/@comment-35289850-20200817213219/@comment-45117243-20200818013249

You can basically change everything via CSS, but the problem is that any change to the HTML (which you have no control on) may need a change in the CSS, so it is recommended to not step too far away or you lose control.

Putting a background image to an element, though, is a simple thing. But take in account that the picture will be cropped on narrow screens, because at least for me handling different screen widths will be hard work that does not worth the subject.