目前的情况是，您正在将选定的媒体项分配给以下行中的所有三个输入：

j(\'#preview-fav, #preview-grav, #preview-thumb\').val(attachment.url);

为了只将值传递给其中一个，需要更改该行以响应按钮中设置的某种标记。在下面的示例中，我设置了data javascript中引用的按钮中的属性。

因此，假设您有以下html：

<!-- upload buttons -->
<input type="button" class="upload-button" data-target="input_1" value="Upload button 1" />
<input type="button" class="upload-button" data-target="input_2" value="Upload button 2" />
<input type="button" class="upload-button" data-target="input_3" value="Upload button 3" />

<!-- inputs to receive the value -->
<input type="text" id="input_1" value="" />
<input type="text" id="input_2" value="" />
<input type="text" id="input_3" value="" />

现在可以在js中执行此操作：

jQuery(function($) {

    $(document).ready(function () {

            var mediaUploader;

            // we can now use a single class name to reference all upload buttons
            $(\'.wp-admin\').on(\'click\', \'.upload-button\', function(e) {

                e.preventDefault();                

                // store the element that was clicked for use later
                trigger = $(this);

                if( mediaUploader ){
                    mediaUploader.open();
                    return;
                }

                mediaUploader = wp.media.frames.file_frame = wp.media({
                    title: \'Upload\', 
                    button: {
                        text: \'Upload\'
                    },
                    multiple: false
                });

                mediaUploader.on(\'select\', function() {

                    attachment = mediaUploader.state().get(\'selection\').first().toJSON();

                    // we\'re replacing this line:
                    //$(\'#preview-fav, #preview-grav, #preview-thumb\').val(attachment.url);

                    // assign the value of attachment to an input based on the data-target value
                    // of the button that was clicked to launch the media browser
                    $(\'#\' + trigger.data(\'target\') ).val(attachment.url);

                    $(\'.favicon-preview, .gravatar-preview, .thumbnail-preview\').css(\'background\',\'url(\' + attachment.url + \')\');
                });

                mediaUploader.open();

            });            

    });

});

更新基于粘贴的代码，您可以通过以下方式提高效率：

function sweetlola_images(){

    $imgs = array(
        \'gravatar\'  => \'img_1\',
        \'thumbnail\' => \'img_2\',
    );

    foreach( $imgs as $name => $id ){

        // get the image
        $url = esc_attr( get_option( $name ) );

        // if there isn\'t one, set $gravatar as empty string
        $url = $url ? $url : \'\';

        //upload button
        echo \'<input type="button" data-target="\' . $id . \'"  value="Upload" class="button button-secondary upload-button" />\';

        //input text field
        echo \'<input type="text" id="\' . $id . \'" name="\' . $name . \'" value="\' . $url . \'" />\';

        if( empty( $url ) ){ //if the value is empty this will show a just the upload button
            echo \'<input type="button" value="Remove" data-remove_target="\' . $id . \'" class="button button-secondary" />\';
        }

        // note
        echo \'<p><i>Idem.<br />Resolução: 89px X 89px</i></p>\'; 

    }
}

将三种图像类型放入$imgs 数组，并使用单个函数生成它们。