I think you've got two elements limiting the size of the banner .logo
as you suggest above, but also .logo-bg
which is currently:
.logo-bg {
background-image: url("./styles/darkfx/theme/images/logo-bg.png");
width: 523px;
height: 117px;
margin-top: 1px;
}
Remove the width restriction from that and .logo
and you get the full image.