Replace the Admin logo on the admin bar

 function dashboard_logo() {
    echo '
        <style type="text/css">
 <a href="https://nockedup.net/mkmcst/forums/search/%23wpadminbar" rel="nofollow" class="hashtag" id="wpadminbar">#wpadminbar</a> <a href="https://nockedup.net/mkmcst/forums/search/%23wp-admin-bar-wp-" rel="nofollow" class="hashtag" id="wp-admin-bar-wp-">#wp-admin-bar-wp-</a>logo>.ab-item {
    padding: 0 7px;
    background-image: url(https://your url) !important;
    background-size: 70%;
    background-position: center;
    background-repeat: no-repeat;
    opacity: 0.8;
}
 <a href="https://nockedup.net/mkmcst/forums/search/%23wpadminbar" rel="nofollow" class="hashtag" id="wpadminbar">#wpadminbar</a> <a href="https://nockedup.net/mkmcst/forums/search/%23wp-admin-bar-wp-" rel="nofollow" class="hashtag" id="wp-admin-bar-wp-">#wp-admin-bar-wp-</a>logo>.ab-item .ab-icon:before {
    content: " ";
    top: 2px;
}
        </style>
    ';
}
add_action('wp_before_admin_bar_render', 'dashboard_logo');