FWIF there is a CSS image replacement method. Suppose the logo is 250px width and height and we have the url of the image, our code to use in Custom CSS option ( from plugin or theme provided) will look like this.
.site-title a {
background: url( "https://dummyimage.com/250x250/000000/ffe0ff.png" );
width: 250px; height: 250px; display: block; margin: 0 auto 50px;
text-indent: 105%; white-space: nowrap; overflow: hidden;
}
Also we can further adjust the size based on screenwidth, make it smaller on small device.