.p-navSticky { background: url("whatever.png") no-repeat center center / cover; }
It's did not work with my SpaceX Style sirYou can set background for it in extra.less:
ACP > Appearance > Styles > Your style > Style properties > Header and navigation > Header/logo rowCSS:.p-navSticky { background: url("whatever.png") no-repeat center center / cover; }