Laravel.io
<?php

use Illuminate\Database\Seeder;
use Backpack\Settings\app\Models\Setting;

class DefaultSettingsSeeder extends Seeder
{
    protected $settings = [
        [
            'key'         => 'pic_1',
            'name'        => 'Image_1',
            'description' => 'Description pic 1',
            'value'       => 'image_url',
            'field'       => '{"name":"value","label":"Active","type":"text"}',
            'active'      => 1,
        ],
       [
            'key'         => 'pic_2',
            'name'        => 'Image_2',
            'description' => 'Description pic 2',
            'value'       => 'image_url',
            'field'       => '{"name":"value","label":"Active","type":"text"}',
            'active'      => 1,
        ],
    ];

    public function run()
    {
        foreach ($this->settings as $index => $setting) {
            $result = Setting::firstOrCreate(['key' => $setting['key']], [
                'name'        => $setting['name'],
                'description' => $setting['description'],
                'value'       => $setting['value'],
                'field'       => $setting['field'],
                'active'      => 1,
            ]);
        }
    }
}

Please note that all pasted data is publicly available.