Replace default icon with an image

He
We try to replace the default icon with an image. we use this css code for this:

#top .fallback-post-type-icon {
content: "";
width: 20px;
height: 20px;
display: inline-block;
vertical-align: middle;
background: url(https://new.fcallmendingen.ch/wp-content/uploads/2020/03/football-157930_640.png) no-repeat center center;
background-size: contain;
}

It works, but now we have both, the old default icon and the new default icon in one.
How we can disable the old default icon?
Thanks very much.
Best regards
Mike